P1516Novel cardiotropic AAV variant C102 vectors show superior gene delivery & reduced immunogenicity in non-human primates, transduction of human cardiomyocytes, & correction of Fabry disease phenotype

Background

Cardiac-targeted gene therapy vectors are needed. Fabry disease is a rare, X-linked disorder caused by mutations in the GLA gene, which encodes α-galactosidase A (GLA). Storage and accumulation of glycolipid substrates of GLA leads to organ damage. Cardiovascular disease is the most common cause of mortality in Fabry disease (75% of deaths). Enzyme replacement therapy (ERT; first line treatment for most patients) demonstrates clearance of Gb3 from capillary endothelial cells. However, Gb3 accumulation in podocytes, cardiomyocytes, and vascular smooth muscle cells persists. Gene replacement strategies leveraging adeno-associated virus (AAV) vectors with high tropism for affected organs (namely the heart) may directly address the underlying pathophysiology of Fabry disease.

Purpose

To unlock the full potential of cardiac gene therapy, novel targeted vectors are needed with enhanced tropism for specific target tissues when delivered in vivo.

Methods

An industrialized “directed evolution” approach (Therapeutic Vector Evolution) was applied in the most relevant animal species (non-human primate; NHP) which led to the discovery of C102, a novel AAV variant capable of efficient gene delivery throughout the primate heart following a single intravenous (IV) administration. C102 biodistribution using a ubiquitous promoter was evaluated in mice and NHP at doses at least 10-fold lower than current AAV-based clinical trials for neuromuscular gene therapy. Animal studies conformed to the NIH Principles of Laboratory Animal Care. To evaluate the ability of the C102 capsid to transduce human target cells relevant to Fabry disease, human pluripotent stem cell-derived cardiomyocytes were transduced. To evaluate the ability of C102 to correct Fabry disease, cultured patient fibroblasts were transduced with the C102.GLA product.

Results

Following a single IV administration in mice, the onset of C102.luciferase expression was rapid (14 days) and durable. Dose-dependent luciferase activity was observed in Fabry disease target tissues, including heart and liver. Following a single IV administration in NHP, superior delivery to heart was demonstrated and immunogenicity was markedly reduced compared to first generation wild-type vectors (AAV8,9), and genomes were present throughout the heart and skeletal muscle groups. In human cardiomyocytes in vitro, C102.EGFP demonstrated significantly higher transduction compared to wild-type AAV1 and 9 vectors (immunofluorescence imaging and quantification by flow cytometry) at all doses. Following transduction with increasing doses of the C102.GLA product in Fabry patient fibroblasts, dose-dependent GLA expression and function was observed.

C102 Genome Delivery in NHP

Conclusion

The data generated using the novel C102 capsid and the C102.GLA Fabry product validate the Therapeutic Vector Evolution approach for cardiac tissue targeting in vivo and provide a strong preclinical data package to enable clinical translation.

Dual-site sampling improved detection rates for MRSA colonization in patients with cutaneous abscesses

Extranasal sites are common reservoirs of Staphylococcus aureus colonization and may be relevant for methicillin-resistant S. aureus (MRSA) screening and infection control strategies. The objective here was to determine whether inguinal specimens could also be screened using Xpert SA Nasal Complete assay for MRSA. Results were compared to broth enrichment culture. Among 162 consented adults seeking care in the emergency department for cutaneous abscesses, inguinal specimens were found positive for MRSA more often than nares specimens, 24% and 26% by PCR or culture, respectively, compared to 19% each by PCR or culture. Overall, 6% of adults colonized with MRSA would have been missed by nares screening alone. Compared to culture, Xpert SA Nasal Complete assay demonstrated sensitivity and specificity of 89% and 97%, respectively, for detecting nares and/or inguinal MRSA colonization. In conclusion, inguinal specimens were a more common reservoir for MRSA than nares specimens in this population of patients.

Launching the Tidal Model: evaluating the evidence

Launching the Tidal Model: evaluating the evidence This paper reports on two evaluations of the Tidal Model, in the context of two separate acute admission wards, one in Birmingham (2004) and the other in Newcastle (2001), and makes recommendations concerning the criteria and type of reasoning appropriate to evaluating the evidence the two projects have generated. In the Birmingham study, results showed that in the year following the introduction of the Tidal Model, the total number of serious untoward incidents such as physical assault, violence and harassment, decreased by 57%. Nurse satisfaction with their work also improved with nurses rating the model superior to their previous way of working. Inpatient service user assessment of the overall quality of their care was also positive. These findings are then compared with the positive results of an earlier study of the Tidal Model undertaken in Newcastle in 2001. That study was criticized, however, for not showing conclusively that the positive results of the evaluation correlated with the introduction of the Tidal Model. This criticism is briefly examined in the light of both ancient (Aristotle) and modern (Charles Peirce) understandings of the nature of evidence and suggests that such criticism begs the question of the nature of proof. The paper concludes by arguing that, according to both Aristotle and the procedures of abductive reasoning advocated by Charles Peirce, inferring a positive correlation between the results of both studies and the introduction of Tidal Model is a good example of reasonable inference to the best explanation. The available evidence suggests that the results of both studies render the conclusion probable and thus 'good enough' to warrant serious consideration for implementing the Tidal Model more widely within and across Mental Health NHS Trusts.

Functional interactions of antiapoptotic proteins and tumor necrosis factor in the context of a replication-competent adenovirus

Replication-selective oncolytic adenoviruses hold promise, but novel mechanisms must be identified to maximize intratumoral virus persistence, spread and therapeutic transgene-carrying capacity while maintaining safety. One of the main approaches to engineering cancer-selectivity has been to delete a viral gene that is theoretically expendable in cancer cells. Results with this approach have been mixed, however, as evidenced by controversy over Onyx-015 (E1B-55kD(-)) selectivity. We hypothesized that the functional redundancy between viral gene products might limit selectivity and/or potency with this approach. Antiviral immune inducers of apoptosis (eg TNF-alpha) have not been thoroughly investigated in previous studies. We therefore explored whether deletion of functionally redundant viral genes, E1B-19kD and E3B, both independently antagonize TNF-alpha, could lead to enhanced oncolytic potency while maintaining selectivity. Since tumors have numerous blocks in apoptotic pathways, we hypothesized that deletion of one or both gene regions would result in cancer-selectivity in the presence of TNF-alpha. We have previously shown that the E1B-19kD deletion resulted in enhanced viral spread in vitro and in immunocompetent tumor models in vivo. In contrast, the impact of E3B deletion, especially its in vitro selectivity and potency, was not thoroughly characterized, although it resulted in rapid immune-mediated viral clearance in vivo. Furthermore, previous publications indicated that double-deleted mutants have selectivity but unsatisfactory efficacy. We compared the selectivity and potency of E1B-19kD(-), E3B(-) and E1B-19kD(-)/E3B(-) mutants to wild-type adenovirus. In cancer cells, the E1B-19kD(-) mutant had superior replication, spread and cytolysis (+) or (-) TNF-alpha; deletion of both E1B-19kD and E3B was relatively deleterious. In normal cells without TNF-alpha, similar results were obtained. In contrast, all three mutants were significantly inhibited in the presence of TNF-alpha. In immunocompetent mice, all three mutants were significantly inhibited in normal tissue. In tumors, only the E1B-19kD(-) mutant demonstrated enhanced replication, spread and antitumoral efficacy. Therefore, E1B-19kD deletion and E3B retention should be incorporated in oncolytic adenoviruses for enhanced safety and efficacy. In addition, functional redundant viral genes and their biological mediators/targets need to be carefully examined for the next generation of gene-deleted oncolytic viruses.

Localization to the nucleolus is a common feature of coronavirus nucleoproteins, and the protein may disrupt host cell division

The subcellular localization of transmissible gastroenteritis virus (TGEV) and mouse hepatitis virus (MHV) (group I and group II coronaviruses, respectively) nucleoproteins (N proteins) were examined by confocal microscopy. The proteins were shown to localize either to the cytoplasm alone or to the cytoplasm and a structure in the nucleus. This feature was confirmed to be the nucleolus by using specific antibodies to nucleolin, a major component of the nucleolus, and by confocal microscopy to image sections through a cell expressing N protein. These findings are consistent with our previous report for infectious bronchitis virus (group III coronavirus) (J. A. Hiscox et al., J. Virol. 75:506-512, 2001), indicating that nucleolar localization of the N protein is a common feature of the coronavirus family and is possibly of functional significance. Nucleolar localization signals were identified in the domain III region of the N protein from all three coronavirus groups, and this suggested that transport of N protein to the nucleus might be an active process. In addition, our results suggest that the N protein might function to disrupt cell division. Thus, we observed that approximately 30% of cells transfected with the N protein appeared to be undergoing cell division. The most likely explanation for this is that the N protein induced a cell cycle delay or arrest, most likely in the G(2)/M phase. In a fraction of transfected cells expressing coronavirus N proteins, we observed multinucleate cells and dividing cells with nucleoli (which are only present during interphase). These findings are consistent with the possible inhibition of cytokinesis in these cells.

Pleuromutilins. Part 1. The identification of novel mutilin 14-carbamates

A novel series of mutilin 14-carbamates has been discovered as a result of structure-activity studies on the naturally occurring antibiotic pleuromutilin (1). In particular, the 4-methoxybenzoylcarbamate, SB-222734 (15o) displays potent antibacterial activity against a number of bacterial pathogens which are resistant to currently used agents and shows enhanced metabolic stability when compared to earlier pleuromutilin derivatives. Such derivatives therefore have the potential to provide a new class of antibacterial agents for human therapy which address the threat of bacterial resistance.

The coronavirus infectious bronchitis virus nucleoprotein localizes to the nucleolus

The coronavirus nucleoprotein (N) has been reported to be involved in various aspects of virus replication. We examined by confocal microscopy the subcellular localization of the avian infectious bronchitis virus N protein both in the absence and in the context of an infected cell and found that N protein localizes both to the cytoplasmic and nucleolar compartments.

An adenovirus E1A mutant that demonstrates potent and selective systemic anti-tumoral efficacy

Replication-selective oncolytic viruses constitute a rapidly evolving and new treatment platform for cancer. Gene-deleted viruses have been engineered for tumor selectivity, but these gene deletions also reduce the anti-cancer potency of the viruses. We have identified an E1A mutant adenovirus, dl922-947, that replicates in and lyses a broad range of cancer cells with abnormalities in cell-cycle checkpoints. This mutant demonstrated reduced S-phase induction and replication in non-proliferating normal cells, and superior in vivo potency relative to other gene-deleted adenoviruses. In some cancers, its potency was superior to even wild-type adenovirus. Intravenous administration reduced the incidence of metastases in a breast tumor xenograft model. dl922-947 holds promise as a potent, replication-selective virus for the local and systemic treatment of cancer.

Anticoagulation in continuous veno-venous haemofiltration

The reasons for introduction of a heparin protocol are explained, with best practice principles of a protocol stated. The pharmacological properties of heparin are explained, and standardisation of monitoring procedures discussed. The responsibilities of the nurse in both laboratory and clinical monitoring of the effects of heparin are discussed. The use of an algorithm to alter heparin dosages against APPT results is justified.

The cell cycle and drug discovery: the promise and the hope

In recent years, there have been major developments in the understanding of the cell cycle. It is now known that normal cellular proliferation is tightly regulated by the activation and deactivation of a series of proteins that constitute the cell cycle machinery. The expression and activity of components of the cell cycle can be altered during the development of a variety of diseases where aberrant proliferation contributes to the pathology of the illness. Apart from yielding a new source of untapped therapeutic targets, it is likely that manipulating the activity of such proteins in diseased states will provide an important route for treating proliferative disorders, and the opportunity to develop a novel class of future medicines.

Altered expression of cell cycle proteins and prolonged duration of cardiac myocyte hyperplasia in p27KIP1 knockout mice

-The precise role of cell cycle-dependent molecules in controlling the switch from cardiac myocyte hyperplasia to hypertrophy remains to be determined. We report that loss of p27(KIP1) in the mouse results in a significant increase in heart size and in the total number of cardiac myocytes. In comparison to p27(KIP1)+/+ myocytes, the percentage of neonatal p27(KIP1)-/- myocytes in S phase was increased significantly, concomitant with a significant decrease in the percentage of G(0)/G(1) cells. The expressions of proliferating cell nuclear antigen, G(1)/S and G(2)/M phase-acting cyclins, and cyclin-dependent kinases (CDKs) were upregulated significantly in ventricular tissue obtained from early neonatal p27(KIP1)-/- mice, concomitant with a substantial decrease in the expressions of G(1) phase-acting cyclins and CDKs. Furthermore, mRNA expressions of the embryonic genes atrial natriuretic factor and alpha-skeletal actin were detectable at significant levels in neonatal and adult p27(KIP1)-/- mouse hearts but were undetectable in p27(KIP1)+/+ hearts. In addition, loss of p27(KIP1) was not compensated for by the upregulation of other CDK inhibitors. Thus, the loss of p27(KIP1) results in prolonged proliferation of the mouse cardiac myocyte and perturbation of myocyte hypertrophy.

Cell cycle regulatory molecules (cyclins, cyclin-dependent kinases and cyclin-dependent kinase inhibitors) and the cardiovascular system; potential targets for therapy?

In the preceding sections we have described the potential for using cell cycle regulatory molecules as targets for drug development within the cardiovascular system. Opportunities for affecting the expression and activities of selected cell cycle regulatory molecules exist in interventional cardiological procedures such as PTCA to limit specifically the intimal hyperplasia of vascular smooth muscle cells that occurs following angioplasty. In addition, the potential for targeting the cardiac myocyte cell cycle to re-initiate cell division in a controlled manner would provide a suitable approach for repairing damaged areas of myocardial tissue following an infarct. Although this approach has not been demonstrated to date in vivo, data from transgenic mouse models and in vitro studies have implicated the cell cycle as a suitable target for manipulation. The next few years will enable the feasibility of this approach to be demonstrated.

Cell cycle profiles and expressions of p21CIP1 AND P27KIP1 during myocyte development

The ability of the cardiac myocyte to divide ceases shortly after birth. Thus, following severe injury, e.g., during myocardial infarction, the mature heart is unable to regenerate new tissue to replace the dead or damaged tissue. The identification of the molecules controlling the cessation of myocyte cell division may lead to therapeutic strategies which aim to re-populate the damaged myocardial area. Hence, we have determined the cell cycle profile, expressions and activities of the cyclin-dependent kinase inhibitors (CDKIs), p21CIP1 and p27KIP1, during rat ventricular myocyte development. Fluorescent activated cell sorting (FACS) analyses showed the percentage of S phase myocytes to be decreased significantly throughout development, concomitant with a significant increase in the percentage of G0/G1 and G2/M phase cells. The expression of p21CIP1 and p27KIP1 increased significantly throughout cardiac development and complexed differentially with a number of cyclins and CDKs. Furthermore, an adult myocyte extract reduced neonatal myocyte CDK2 kinase activity significantly (>30%, p<0.05) whereas immunodepletion of p21CIP1 from adult lysates restored CDK2 kinase activity. Thus, p21CIP1 and p27KIP1 may be important for the withdrawal of cardiac myocytes from the cell cycle and for maintaining the G0/G1 and G2/M phase blockades.

Expressions and activities of cell cycle regulatory molecules during the transition from myocyte hyperplasia to hypertrophy

The role of cell cycle dependent molecules in controlling the switch from cardiac myocyte hyperplasia to hypertrophy remains unclear, although in the rat this process occurs between day 3 and 4 after birth. In this study we have determined (1) cell cycle profiles by fluorescence activated cell sorting (FACS); and (2) expressions, co-expressions and activities of a number of cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors by reverse transcriptase-polymerase chain reaction (RT-PCR), immunoblotting and in vitro kinase assays in freshly isolated rat cardiac myocytes obtained from 2, 3, 4 and 5-day-old animals. The percentage of myocytes found in the S phase of the cell cycle decreased significantly during the transition from hyperplasia to hypertrophy (5.5, 3.5, 2.3 and 1.9% of cells in 2-, 3-, 4- and 5-day-old myocytes, respectively,P<0.05), concomitant with a significant increase in the percentage of G0/G1 phase cells. At the molecular level, the expressions and activities of G1/S and G2/M phase acting cyclins and CDKs were downregulated significantly during the transition from hyperplasia to hypertrophy, whereas the expressions and activities of G1 phase acting cyclins and CDKs were upregulated significantly during this transition. In addition, p21(CIP1)- and p27(KIP1)- associated CDK kinase activities remained relatively constant when histone H1 was used as a substrate, whereas phosphorylation of the retinoblastoma protein was upregulated significantly during the transition from hyperplasia to hypertrophy. Thus, there is a progressive and significant G0/G1 phase blockade during the transition from myocyte hyperplasia to hypertrophy. Whilst CDK2 and cdc2 may be pivotal in the withdrawal of cardiac myocytes from the cell cycle, CDK4 and CDK6 may be critical for maintaining hypertrophic growth of the myocyte during development.

Role of G1 phase cyclins and cyclin-dependent kinases during cardiomyocyte hypertrophic growth in rats

Cell cycle regulatory molecules are implicated in cardiomyocyte hypertrophy. We have investigated protein expression of cyclins A, D1-3, and E and cyclin-dependent kinases (CDKs) 2, 4, 5, and 6 in left ventricular (LV) tissues during the development of LV hypertrophy in rats following aortic constriction (AC). Compared with their expression in sham-operated controls (SH), expression of cyclins D2 and D3 and of CDK4 and CDK6 increased significantly from day 3 to day 21 after AC concomitant with increased LV mass. However, no significant difference was observed for CDK2 or CDK5. Cyclins A, D1, and E were undetectable. In vitro kinase activities of CDK4 and CDK6 increased approximately 70% from day 7 to day 14 in AC myocytes compared with SH myocytes (P < 0.03). Fluorescence-activated cell sorter analysis revealed a G0/G1 to G2/M phase progression in AC myocyte nuclei (22.0 +/- 1.1% in G2/M) by day 7 postoperation compared with progression in SH myocyte nuclei (14.0 +/- 0.8% in G2/M; P < 0.01). Thus an upregulation of certain cell cycle regulators is associated with cardiomyocyte hypertrophy.

Arresting developments in the cardiac myocyte cell cycle: role of cyclin-dependent kinase inhibitors

Like most other cells in the body, foetal and neonatal cardiac myocytes are able to divide and proliferate. However, the ability of these cells to undergo cell division decreases progressively during development such that adult myocytes are unable to divide. A major problem arising from this inability of adult cardiac myocytes to proliferate is that the mature heart is unable to regenerate new myocardial tissue following severe injury, e.g. infarction, which can lead to compromised cardiac pump function and even death. Studies in proliferating cells have identified a group of genes and proteins that controls cell division. These proteins include cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors (CDKIs), which interact with each other to form complexes that are essential for controlling normal cell cycle progression. A variety of other proteins, e.g. the retinoblastoma protein (pRb) and members of the E2F family of transcription factors, also can interact with, and modulate the activities of, these complexes. Despite the major role that these proteins play in other cell types, little was known until recently about their existence and activities in immature (proliferating) or mature (non-proliferating) cardiac myocytes. The reason(s) why cardiac myocytes lose their ability to divide during development remains unknown, but if strategies were developed to understand the mechanisms underlying cardiac myocyte growth, it could open up new avenues for the treatment of cardiovascular disease. In this article, we shall review the function of the cell cycle machinery and outline some of our recent findings pertaining to the involvement of the cell cycle in modulating cardiac myocyte growth and hypertrophy.

Can shoulder dystocia be predicted? Preconceptive and prenatal factors

OBJECTIVE

To evaluate the predictability of shoulder dystocia using preconceptive and prenatal risk factors.

STUDY DESIGN

Data from 1,622 term patients with prenatal care prior to 20 weeks who delivered single, vertex fetuses during a consecutive 12-month period were analyzed. Two groups were chosen. The first group was patients whose fetuses experienced shoulder dystocia during delivery (cases). The second group (controls) consisted of the remaining patients, whose fetuses had not experienced shoulder dystocia. The two groups were compared with regard to demographics and pregnancy characteristics.

RESULTS

Factors not significantly different between the two groups included were obesity, multiparity, history of diabetes, short maternal stature, postdatism and advanced maternal age. The incidence of macrosomia was significantly higher (P < .001) in cases (35.4%) than in controls (4.8%). Other factors associated with shoulder dystocia were previous shoulder dystocia, concurrent diabetes, prior delivery of a fetus > 4,000 g and excessive weight gain during pregnancy. Many factors previously associated with shoulder dystocia were found to be nonsignificant in our study.

CONCLUSION

Macrosomia appears to be the single important factor associated with shoulder dystocia which, even in the presence of significant risk factors, remains largely unpredictable.

Diacylglycerol-induced protection against injury during ischemia and reperfusion in the rat heart: comparative studies with ischemic preconditioning

The role of protein kinase C (PKC) activation in ischemic preconditioning remains controversial. Since diacylglycerol is the endogenous activator of PKC and as such might be expected cardioprotective, we have investigated whether: (i) the diacylglycerol analog 1,2-dioctanoyl-sn-glycerol (DOG) can protect against injury during ischemia and reperfusion; (ii) any effect is mediated via PKC activation; and (iii) the outcome is influenced by the time of administration. Isolated rat hearts were perfused with buffer at 37 degrees C and paced at 400 bpm. In Study 1, hearts (n=6/group) were subjected to one of the following: (1) 36 min aerobic perfusion (controls); (2) 20 min aerobic perfusion plus ischemic preconditioning (3 min ischemia/3 min reperfusion+5 min ischemia/5 min reperfusion); (3) aerobic perfusion with buffer containing DOG (10 microM) given as a substitute for ischemic preconditioning; (4) aerobic perfusion with DOG (10 microM) during the last 2 min of aerobic perfusion. All hearts then were subjected to 35 min of global ischemia and 40 min reperfusion. A further group (5) were perfused with DOG (10 microM) for the first 2 min of reperfusion. Ischemic preconditioning improved postischemic recovery of LVDP from 24+/-3% in controls to 71+/-2% (P < 0.05). Recovery of LVDP also was enhanced by DOG when given just before ischemia (54+/-4%), however, DOG had no effect on the recovery of LVDP when used as a substitute for ischemic preconditioning (22+/-5%) or when given during reperfusion (29+/-6%). In Study 2, the first four groups of study were repeated (n=4-5/group) without imposing the periods of ischemia and reperfusion, instead hearts were taken for the measurement of PKC activity (pmol/min/mg protein+/-SEM). PKC activity after 36 min in groups (1), (2), (3) and (4) was: 332+/-102, 299+/-63, 521+/-144, and 340+/-113 and the membrane:cytosolic PKC activity ratio was: 5.6+/-1.5, 5.3+/-1.8, 6.6+/-2.7, and 3.9+/-2.1 (P=NS in each instance). In conclusion, DOG is cardioprotective but under the conditions of the present study is less cardioprotective than ischemic preconditioning, furthermore the protection does not appear to necessitate PKC activation prior to ischemia.

Arterial disease and thrombosis in the antiphospholipid syndrome: a pathogenic role for endothelin 1

OBJECTIVE

To explore a possible correlation between endothelin 1 (ET-1), the most potent endothelium-derived contracting factor that modulates vascular smooth muscle tone, and arterial disease in patients with the antiphospholipid syndrome (APS).

METHODS

Plasma levels of ET-1 were measured in APS patients with (n = 16) and without (n = 11) arterial thrombosis and in non-APS patients with arterial thrombosis (n = 9). In addition, steady-state prepro-ET-1 messenger RNA (mRNA) levels were determined in endothelial cells treated with a range of human monoclonal anticardiolipin antibodies (aCL) (as anti-beta2-glycoprotein I antibodies) by semiquantitative 32P-dCTP-labeled reverse transcription-polymerase chain reaction.

RESULTS

Compared with healthy controls, markedly increased plasma levels of ET-1 were found in APS patients with arterial thrombosis (2.00 +/- 0.87 versus 0.96 +/- 0.37 pg/ml; P = 0.0001) but not in other groups. Three human monoclonal aCL induced prepro-ET-1 mRNA levels significantly more than did control monoclonal antibody lacking aCL activity.

CONCLUSION

Plasma ET-1 levels correlated significantly with a history of arterial thrombosis in patients with APS. Prepro-ET-1 mRNA was induced by human monoclonal aCL in the in vitro experimental system. The induction of ET-1 by antiphospholipid antibodies might contribute to increased arterial tone, leading to vasospasm and, ultimately, to arterial occlusion.

Differential changes in transforming growth factor-beta isoform expression during postnatal cardiac growth

Transforming growth factor-beta (TGF-beta) is synthesised as an inactive precursor protein; this is cleaved to produce the mature peptide and a latency associated protein (LAP), which remains associated with the mature peptide until activation by LAP degradation. Isoform specific antibodies raised against the LAPs for TGF-beta 2 and -beta 3 were used to determine the myocardial levels of LAP (activatable TGF-beta) and full length precursor (inactive TGF-beta) forms during post-natal development in the rat. TGF-beta 2 was present predominantly as the precursor in 2 day old myocardium. There was an age-dependent shift from precursor protein to LAP between 2 and 28 days. A corresponding increase in the level of mature (activatable) TGF-beta 2 was found. TGF-beta 3 was detected in significant quantities only as LAP. However, a four-fold increase in the expression of TGF-beta 3 LAP was observed between 2 and 28 days. The substantial increases in activatable forms of TGF-beta 2 and -beta 3 that occur in myocardium during the first 28 days of life in the rat support a role for these proteins in post-natal cardiac development.

The efficacy and safety of salmeterol compared to theophylline: meta-analysis of nine controlled studies

The aim of this study was to compare the efficacy and safety of salmeterol vs theophylline in asthma management using meta-analysis of clinical trials. Nine clinical studies, containing a total of 1330 patients, met meta-analysis inclusion criteria: randomized, controlled study, minimum 2-week treatment duration with either salmeterol or theophylline. The main outcome measurements were morning and evening peak expiratory flow rate (PEFR), morning and evening symptom scores, use of salbutamol as rescue medication, and withdrawal from treatment for any cause. During the second week of treatment, salmeterol patients had a 10 l min-1 greater increase in mean morning PEFR from baseline than theophylline patients (P < 0.001). Similarly, in the second week, the increase in mean evening PEFR from baseline observed with salmeterol was significantly greater (P < 0.01) than that observed with theophylline. Salmeterol also produced a significantly greater increase in mean morning and evening PEFR than theophylline at weeks 3 and 4. Patients receiving salmeterol were free from daytime symptoms for a mean of 51% of days in the second week compared to 39% for theophylline patients (P < 0.001). Salmeterol patients experienced a mean of 63% symptom-free nights compared to 52% for theophylline patients (P < 0.001). Rescue medication with salbutamol was not required on 49% of days for salmeterol patients and 34% of days for theophylline patients. All results were maintained in the third and fourth weeks of treatment. Withdrawal and incidence of adverse events leading to withdrawal were significantly less frequent in patients receiving salmeterol (P < 0.001). Thus, this meta-analysis suggests that salmeterol has a superior safety and efficacy profile to theophylline in the management of symptoms of chronic asthma.

Downregulation of cyclin-dependent kinase inhibitors p21 and p27 in pressure-overload hypertrophy

We postulated that the cyclin-dependent kinase inhibitors p21 and p27 could regulate the alterations in growth potential of cardiomyocytes during left ventricular hypertrophy (LVH). LVH was induced in adult rat hearts by aortic constriction (AC) and was monitored at days 0, 1, 3, 7, 14, 21, and 42 postoperation. Relative to sham-operated controls (SH), left ventricle (LV) weight-to-body weight ratio in AC increased progressively with time without significant differences in body weight or right ventricle weight-to-body weight ratio. Atrial natriuretic factor mRNA increased significantly in AC to 287% at day 42 compared with SH (P < 0.05), whereas p21 and p27 mRNA expression in AC rats decreased significantly by 58% (P < 0.03) and 40% (P < 0.05) at day 7, respectively. p21 and p27 protein expression decreased significantly from days 3 to 21 in AC versus SH, concomitant with LV adaptive growth. Immunocytochemistry showed p21 and p27 expression in cardiomyocyte nuclei. Thus downregulation of p21 and p27 may modulate the adaptive growth of cardiomyocytes during pressure overload-induced LVH.

Differential protein expression and subcellular distribution of TGFbeta1, beta2 and beta3 in cardiomyocytes during pressure overload-induced hypertrophy

The transforming growth factor beta (TGFbeta) superfamily plays an important role in the myocardial response to hypertrophy. We have investigated the protein expression of TGFbeta1, beta2 and beta3 in left ventricular tissue, and determined their subcellular distribution in myocytes by immunoblotting and immunocytochemistry during the development of left ventricular hypertrophy (LVH), using isoform specific antibodies to TGFbeta1, beta2 and beta3. LVH was produced in rats by aortic constriction (AC) and LV tissue was obtained at days (d)0, 1, 3, 7, 14, 21 and 42 following operation. Compared with age matched sham-operated controls (SH), TGFbeta1 levels in LV tissue of AC rats increased significantly from d1-d14 (P<0.03) concomitant with the adaptive growth of LV tissue. In contrast, TGFbeta3 levels decreased in LV tissue of AC rats from d3 post-operation (significant from d14-d42, P<0.03). No significant difference in TGFbeta2 levels were observed from SH and AC rats after operation. Antibodies to TGFbeta1 stained intercalated disks, sarcolemmal membranes and cytoplasm, but not nuclei, of cardiomyocytes on LV sections from untreated and SH rats. However, a trans-localisation of TGFbeta1 to the nuclei of cardiomyocytes was observed in AC hearts. Antibodies to TGFbeta3 stained T tubules, cytoplasm and the nuclei of cardiomyocytes from untreated and SH rats. However, by d7 post-AC operation, TGFbeta3 expression was lost rapidly from nuclei of cardiomyocytes followed by a reduction in total TGFbeta3 immunofluorescence in myocytes. Antibodies to TGFbeta2 stained sarcolemmal membranes of cardiomyocytes from both SH and AC rats without significant difference between groups. Thus, the differential pattern of protein expression and subcellular distribution of TGFbeta1, beta2 and beta3 in myocytes during the development of LVH suggests that these molecules play different roles in the response of cardiomyocytes to LVH.

Phorbol ester, but not ischemic preconditioning, activates protein kinase D in the rat heart

The signal transduction pathways that mediate the cardioprotective effects of ischemic preconditioning remain unclear. Here we have determined the role of a novel kinase, protein kinase D (PKD), in mediating preconditioning in the rat heart. Isolated rat hearts (n=6/group) were subjected to either: (i) 36 min aerobic perfusion (control); (ii) 20 min aerobic perfusion plus 3 min no-flow ischemia, 3 min reperfusion, 5 min no-flow ischemia, 5 min reperfusion (ischemic preconditioning); (iii) 20 min aerobic perfusion plus 200 nmol/l phorbol 12-myristate 13-acetate (PMA) given as a substitute for ischemic preconditioning. The left ventricle then was excised, homogenized and PKD immunoprecipitated from the homogenate. Activity of the purified kinase was determined following bincubation with [gamma32P]-ATP+/-syntide-2, a substrate for PKD. Significant PKD autophosphorylation and syntide-2 phosphorylation occurred in PMA-treated hearts, but not in control or preconditioned hearts. Additional studies confirmed that recovery of LVDP was greater and initiation of ischemic contracture and time-to-peak contracture were less, in ischemic preconditioned hearts compared with controls (P<0.05). Our results suggest that the early events that mediate ischemic preconditioning in the rat heart occur via a PKD-independent mechanism.

Expression and activities of cyclins and cyclin-dependent kinases in developing rat ventricular myocytes

The molecular mechanisms responsible for the alterations in proliferative capacity of cardiac myocytes during development remain unknown; however, cell cycle dependent molecules may be involved. We have determined the expression of cyclins A, D1-3 and E, and cyclin-dependent kinases (CDKs) 2, 4, 5 and 6 and cdc2 in freshly isolated rat cardiac myocytes from fetal (18 days gestation), neonatal (2 days post-natal) and adult animals by immunoblotting. Our results show a dramatic decrease in expression of these proteins during normal cardiac development, such that levels are highest in fetal myocytes but are significantly down-regulated in adult cells (P<0.05, in each case). We also have determined the in vitro kinase activities of cdc2, CDK2, CDK4, CDK5 and CDK6 immunocomplexes in fetal, neonatal and adult myocytes. There was a consistent and significant loss of cdc2, CDK2, CDK4 and CDK6 kinase activities in adult cardiac cell lysates (5.3-, 10.6-, 1.5- and 1.9-fold decreases, respectively) when compared to neonatal samples (P<0.05); CDK5 activity showed a similar trend but failed to reach significance. In conclusion, our results show that the expression and activities of various positive regulators of the cell cycle are down-regulated significantly during development of the cardiac myocyte, concomitant with the loss of proliferative capacity in adult myocytes. Down-regulation of these proteins may be pivotal in the withdrawal of the cardiac myocyte from the cell cycle.

Expression and regulation of 80K/MARCKS, a major substrate of protein kinase C, in the developing rat heart

OBJECTIVE

Protein kinase C (PKC) plays a pivotal role in modulating the growth and differentiation of many cell types including the cardiac myocyte. However, little is known about molecules that act immediately downstream of PKC in the heart. In this study we have investigated the expression of 80K/MARCKS, a major PKC substrate, in whole ventricles and in cardiac myocytes from developing rat hearts.

METHODS

Poly A/ RNA was prepared from neonatal (2-day) and adult (42-day) cardiac myocytes and whole ventricular tissue and mRNA expression determined by reverse transcription-polymerase chain reaction (RT-PCR) using primers designed to identify a 420 bp fragment in the 80K/MARCKS gene. Protein extracts were prepared from either 2-day and 42 day cardiac myocytes or from whole ventricular tissue at 2, 5-11, 14, 17, 21, 28 and 42 days of age. Protein expression was determined by immunoblotting with an 80/MARCKS antipeptide antibody and PKC activity was determined by measuring the amount of gamma 32 P-ATP transferred to a specific peptide substrate.

RESULTS

RT-PCR analysis of 80K/MARCKS mRNA in neonatal (2-day) and adult (42-day) cardiac myocytes showed the expression of this gene in both cell types. Immunoblotting revealed maximum 80K/MARCKS protein expression in whole ventricular tissue at 5 days (a 75% increase above values at 2 days), followed by a transient decrease in expression during the 6-8 day period (61% of the protein expressed at 2 days for 8-day tissue) with levels returning to 5 day levels by 11 days of age. 80K/MARCKS protein was present in cardiac myocytes at 2 days of age whereas it was not detectable in adult cells. In addition, PKC activity levels increased to 160% of levels present at 2 days in 8-day old ventricles with PKC activity levels returning to 5-day levels by 9 days of age. This was then; followed by a steady decline in both 80K/MARCKS protein expression and PKC activity through to adulthood.

CONCLUSIONS

Expression of the PKC substrate, 80K/MARCKS, in cardiac myocytes changes significantly during development and the transient loss of immunoreactive protein during the 6-8 day development period may reflect 80K/MARCKS phosphorylation and subsequent down-regulation as a result of the concomitant up-regulation of PKC activity at this time.