Summary Background Cardiomyopathy is a leading cause of death in patients with Duchenne muscular dystrophy and myocardial damage precedes decline in left ventricular systolic function. We tested the efficacy of eplerenone on top of background therapy in patients with Duchenne muscular dystrophy with early myocardial disease. Methods In this randomised, double-blind, placebo-controlled trial, boys from three centres in the USA aged 7 years or older with Duchenne muscular dystrophy, myocardial damage by late gadolinium enhancement cardiac MRI and preserved ejection fraction received either eplerenone 25 mg or placebo orally, every other day for the first month and once daily thereafter, in addition to background clinician-directed therapy with either angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB). Computer-generated randomisation was done centrally using block sizes of four and six, and only the study statistician and the investigational pharmacy had the preset randomisation assignments. The primary outcome was change in left ventricular circumferential strain (Ecc) at 12 months, a measure of contractile dysfunction. Safety was established through serial serum potassium levels and measurement of cystatin C, a non-creatinine measure of kidney function. This trial is registered with ClinicalTrials.gov, number NCT01521546. Findings Between Jan 26, 2012, and July 3, 2013, 188 boys were screened and 42 were enrolled. 20 were randomly assigned to receive eplerenone and 22 to receive placebo, of whom 20 in the eplerenone group and 20 in the placebo group completed baseline, 6-month, and 12-month visits. After 12 months, decline in left ventricular circumferential strain was less in those who received eplerenone than in those who received placebo (median ΔEcc 1.0 [IQR 0.3–2.2]vs2.2 [1.3–3.1]; p=0.020). Cystatin C concentrations remained normal in both groups, and all non-haemolysed blood samples showed normal potassium concentrations. One 23-year-old patient in the placebo group died of fat embolism, and another patient in the placebo group withdrew from the trial to address long-standing digestive issues. All other adverse events were mild: short-lived headaches coincident with seasonal allergies occurred in one patient given eplerenone, flushing occurred in one patient given placebo, and anxiety occurred in another patient given placebo. Interpretation In boys with Duchenne muscular dystrophy and preserved ejection fraction, addition of eplerenone to background ACEI or ARB therapy attenuates the progressive decline in left ventricular systolic function. Early use of available drugs warrants consideration in this population at high risk of cardiac death, but further studies are needed to determine the effect of combination cardioprotective therapy on event-free survival in Duchenne muscular dystrophy. Funding BallouSkies, Parent Project for Muscular Dystrophy, US National Center for Advancing Translational Sciences, and US National Institutes of Health.
Exposure of vascular endothelial cells to fluid mechanical forces can modulate the expression of many genes involved in vascular physiology and pathophysiology. Here, we report that platelet-derived growth factor (PDGF) A-chain gene expression is induced at the level of transcription in cultured bovine aortic endothelial cells exposed to a physiologic level of steady laminar shear stress (10 dyn/cm2). 5' Deletion analysis of the human PDGF-A promoter revealed that a GC-rich region near the TATA box was required for shear-inducible reporter gene expression. This element conferred shear inducibility onto a heterologous promoter-reporter construct that was otherwise unresponsive to shear stress. The induction of PDGF-A expression by shear was preceded by rapid and transient induction in the expression of the immediate-early gene, egr-1, which binds to GC-rich sequences. Gel shift studies indicated that shear-induced Egr-1 bound to the proximal PDGF-A promoter in a specific and time-dependent manner, displacing Sp1 from their overlapping recognition elements. Overlapping consensus binding sites for Egr-1 and Sp1 also appear in the proximal promoters of several other endothelial genes, including transforming growth factor-beta 1 and tissue factor, whose expression is modulated by shear stress. These findings define the Egr-1 binding site in the proximal PDGF-A promoter as a shear-stress-responsive element and suggest that shear-stimulated Egr-1 gene expression may be a unifying theme in the induction of various other endothelial genes exposed to biomechanical forces.
A sixth member of the mammalian adenylyl cyclase family has been isolated from a canine cardiac cDNA library. This isoform is more highly homologous to type V than to the other adenylyl cyclase types; sequence similarity is apparent even in the transmembrane regions where the greatest divergence among the types exists. Type VI mRNA expression is most abundant in heart and brain; however, unlike type V, a low level ofexpression is also observed in a variety of other tissues examined. Type VI adenylyl cyclase can be stimulated by NaF, guanosine 5'-[rthio]triphosphate, and forskolin but not by Ca2+/calmodulin, whereas it is inhibited by adenosine and its analogues. Comparison of both their structural and biochemical properties suggests that ypes V and VI constitute a distinct subgroup of the mammalian adenylyl cyclase family.Since the cloning of the first mammalian adenylyl cyclase cDNA, four additional adenylyl cyclase cDNAs have been isolated (1)(2)(3)(4)(5). Although each has a distinct tissue distribution and biochemical characteristics, the proteins they encode share the same topology: tandem repetition of a hydrophobic putative transmembrane domain that spans the membrane six times, followed by a large hydrophilic cytoplasmic domain. The amino acid sequence of the cytoplasmic domain is relatively well conserved among the family members; this region also shows homology to other cyclases, such as guanylyl cyclase (6) or adenylyl cyclases from lower eukaryotes (7). However, the amino acid sequence differs significantly in the transmembrane regions of the different adenylyl cyclase types (4). The degree ofthis divergence differs among different members; type II adenylyl cyclase is more homologous to type IV than to other types, whereas type I and III share a lesser degree of homology with the others. Two of the adenylyl cyclases (types II and IV) are similar not only in their amino acid sequence but also in their structure and function; both have a truncated C-terminal tail and lack calmodulin sensitivity. Their tissue distribution, however, is different. This greater degree of similarity between types II and IV suggests that certain adenylyl cyclase isoforms might constitute subclasses within the adenylyl cyclase family.We have recently cloned a cardiac adenylyl cyclase (type V), which appears to be limited in its expression to heart and neural tissue (5). We now describe a type VI adenylyl cyclase; ¶ it exhibits a much higher degree of homology, both in sequence and structure, with type V adenylyl cyclase than with the other known family members. Furthermore, its tissue distribution and biochemical features are also similar. Types V and VI may therefore form a subclass within the mammalian adenylyl cyclase family.
The thymus begins involution in childhood and historically it was thought to be nonfunctional by adulthood, thus presenting no contraindication to the routine practice of thymectomy during cardiothoracic surgery. More recent data suggest, however, that the thymus remains active into adulthood and is responsible for the low-level production of normal T cells. We hypothesize, therefore, that incidental thymectomy during cardiothoracic surgery in infancy causes long-term changes in the cellular immune system. To investigate this hypothesis, we quantified peripheral T-cell subsets and T-cell recombination excision circles in children with congenital heart disease to measure the impact of cardiothoracic surgical procedures and thymectomy performed during a period of immunologic development. We found that cardiothoracic surgical procedures, especially if they include thymectomy, impair T-cell production and produce long-term decreases in total lymphocyte count and CD4(+) and CD8(+) T-cell subsets, suggesting that long-term maintenance of lymphocyte populations is disturbed.
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