AimsNeuregulin-1 (NRG-1) plays a critical role in the adaptation of the heart to injury, inhibiting apoptosis and inducing cardiomyocyte proliferation. We have shown previously that rhNRG-1 improves cardiac function and survival in animal models of cardiomyopathy. Here we report the first human study aimed at exploring the acute and chronic haemodynamic responses to recombinant human NRG-1 (beta 2a isoform; rhNRG-1) in patients with stable chronic heart failure (CHF). Methods and resultsFifteen patients (age, 60 + 2; NYHA II:III, 9:6; left ventricular ejection fraction (LVEF) ,40%) on optimal medical therapy for CHF, received a rhNRG-1 infusion daily for 11 days. Acute and chronic haemodynamic, structural and biochemical effects were determined by serial right heart catheterization, cardiac magnetic resonance (CMR), echocardiography and measurement of neurohumoral indices. Acutely, cardiac output increased by 30% during a 6 h rhNRG-1 infusion (P , 0.01). Pulmonary artery wedge pressure and systemic vascular resistance decreased 30 and 20%, respectively, at 2 h (P , 0.01). A 47% reduction in serum noradrenaline, a 55% reduction in serum aldosterone and a 3.6-fold increase in N-terminal prohormone brain natriuretic peptide levels were concurrently observed (P , 0.001). These acute haemodynamic effects were sustained, as demonstrated by the 12% increase in LVEF from 32.2 + 2.0% (baseline) to 36.1 + 2.3% (mean + SE, P , 0.001) at 12 weeks. The therapy was well tolerated. ConclusionrhNRG-1 appears to produce favourable acute and chronic haemodynamic effects in patients with stable CHF on optimal medical therapy. Randomized controlled trials of rhNRG-1 in cardiac disease are thus warranted. Clinical Trial Registration InformationThe trial was registered with the Australian New Zealand Clinical Trials

Utilizing an in vitro model system of cardiac muscle cell hypertrophy, we have identified a retinoic acid (RA)-mediated pathway that suppresses the acquisition of specific features of the hypertrophic phenotype after exposure to the a-adrenergic receptor agonist phenylephrine. RA at physiological concentrations suppresses the increase in cell size and induction of a genetic marker for hypertrophy, the atrial natriuretic factor (ANF) gene. RA also suppresses endothelin 1 pathways for cardiac muscle cell hypertrophy, but it does not affect the increase in cell size and ANF expression induced by serum stimulation. A trans-activation analysis using a transient transfection assay reveals that neonatal rat ventricular myocardial cells express functional RA receptors of both the retinoic acid receptor and retinoid X receptor (RAR and RXR) subtypes. Using synthetic agonists of RA, which selectively bind to RXR or RAR, our data indicate that RAR/RXR heterodimers mediate suppression of a-adrenergic receptor-dependent hypertrophy. These results suggest the possibility that a pathway for suppression of hypertrophy may exist in vivo, which may have potential therapeutic value.

Maintenance of genomic integrity is an essential cellular function. We previously reported that the transcription factor and tumor suppressor CCAAT/enhancer binding protein δ (C/EBPδ, CEBPD; also known as "NFIL-6β") promotes genomic stability. However, the molecular mechanism was not known. Here, we show that C/EBPδ is a DNA damage-induced gene, which supports survival of mouse bone marrow cells, mouse embryo fibroblasts (MEF), human fibroblasts, and breast tumor cells in response to the DNA cross-linking agent mitomycin C (MMC). Using gene knockout, protein depletion, and overexpression studies, we found that C/EBPδ promotes monoubiquitination of the Fanconi anemia complementation group D2 protein (FANCD2), which is necessary for its function in replication-associated DNA repair. C/EBPδ interacts with FANCD2 and importin 4 (IPO4, also known as "Imp4" and "RanBP4") via separate domains, mediating FANCD2-IPO4 association and augmenting nuclear import of FANCD2, a prerequisite for its monoubiquitination. This study identifies a transcription-independent activity of C/EBPδ in the DNA damage response that may in part underlie its tumor suppressor function. Furthermore, we report a function of IPO4 and nuclear import in the Fanconi anemia pathway of DNA repair.Fanconi anemia | DNA repair | mitomycin C | importin 4 | protein adaptor

The cardiac myosin light chain-2 (MLC-2) gene promoter contains several positive and negative cis-acting sequences that are involved in the regulation of its expression. We describe here the properties of two activator sequences, elements A and P, and their DNA-binding factors (ABFs). Element A (CCAAAAGTGG), located at -61, has homology with the evolutionarily conserved sequence CC(A/T)6GG, present in the genes of many contractile proteins. Element P (TAACCTTGAAAGC), located 114 bp upstream of element A, is conserved in both chicken and rat cardiac MLC-2 gene promoters. Deletion mutagenesis demonstrated that these two elements are involved in the positive regulation of MLC-2 gene transcription. At least two sequence-specific element A-binding proteins, ABF-1 and ABF-2, were identified by gel shift analysis of the fractionated cardiac nuclear proteins. ABF-1 binds to element A with strict dependence on the internal element A sequence AAAAGT. In contrast, ABF-2 exhibits a relaxed sequence requirement, as it recognizes the consensus CArG and CCAAT box sequences as well. ABF-2 also recognizes the distal element P despite the fact that the sequences of elements A and P are divergent. DNase I footprinting, methylation interference, and gel shift analyses demonstrated unequivocally that the element A-DNA affinity-purified protein ABF-2 binds to element P with sequence specificity. Since both elements A and P play a positive regulatory role in MLC-2 gene transcription and bind to a single protein (ABF-2), it would appear that ABF-2 is a key transcription factor with the ability to recognize divergent sequence elements involved in a common regulatory pathway during myogenesis.Eukaryotic genes are regulated primarily at the level of transcription initiation, which involves specific interactions between regulatory nuclear proteins and target gene sequence elements (see references 4, 26, and 29 for review). DNA-protein interactions in eukaryotic promoters are complex, as transcription may need to be regulated positively as well as negatively in both a temporal and spatial manner in response to developmental and environmental signals. It is now known that in many cases, multiple nuclear proteins recognize a single DNA element and thereby introduce a considerable degree of functional diversity to the promoter (1,12,34,40). It is also known that nuclear proteins which exhibit relaxed stringency in DNA binding are involved in the regulation of transcription (6, 9, 37). The functional significance of degenerate-sequence recognition in transcriptional regulation is not yet clear.The genes for muscle contractile proteins are differentially expressed in different muscle and nonmuscle cell types and provide a useful system for investigation of regulatory mechanisms (see references 15, 39, and 43 for review). Recent studies on the genes of muscle contractile protein have led to the identification of potential cis-acting regulatory sequences. Among these sequence elements, the motif CC(AI T)6GG (CArG box or C/BAR) is found at least on...

rhNRG-1 given together with other activators of prosurvival pathways improves preservation of the rat heart and shows promise for increasing the cold-ischemic life of donor hearts in transplantation.