Victor Chang Cardiac Research Institute

About: Victor Chang Cardiac Research Institute is a nonprofit organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Mechanosensitive channels & Heart failure. The organization has 708 authors who have published 1599 publications receiving 70035 citations.

δ Tryptase Is Expressed in Multiple Human Tissues, and a Recombinant Form Has Proteolytic Activity

Abstract: Tryptases are neutral serine proteases selectively expressed in mast cells and have been implicated in the development of a number of inflammatory diseases including asthma. It has recently been established that the number of genes encoding human mast cell tryptases is much larger than originally believed, but it is not clear how many of these genes are expressed. A recent report suggested that the transcript for at least one of these genes, originally named mMCP-7-like tryptase, is not expressed. To further address this question, we screened tissue-specific RNA samples by RT-PCR, using primers designed to match the putative exonic sequence of this gene. We successfully generated and cloned the correctly sized RT-PCR product from mRNA isolated from the human mast cell-I cell line. Two distinct clones were identified whose nucleotide sequence matched the published sequence of the mMCP-7-like I and mMCP-7-like II genes. Transcripts were detected in a wide variety of human tissues including lung, heart, stomach, spleen, skin, and colon. A polyclonal antipeptide Ab that specifically recognizes the translated product of this transcript was used to demonstrate its expression in mast cells that reside in the colon, lung, and inflamed synovium. A recombinant form of this protein expressed in bacterial cells was able to cleave a synthetic trypsin-sensitive substrate, D-Ile-Phe-Lys pNA. These results suggest that the range of functional tryptases is larger than previously recognized. For simplicity, we suggest that the gene, transcripts, and corresponding protein product be named delta tryptase.

Characterization of plasma labile heme in hemolytic conditions.

Abstract: Extracellular hemoglobin, a byproduct of hemolysis, can release its prosthetic heme groups upon oxidation. This produces metabolically active heme that is exchangeable between acceptor proteins, macromolecules and low molecular weight ligands, termed here labile heme. As it accumulates in plasma labile heme acts in a pro-oxidant manner and regulates cellular metabolism while exerting pro-inflammatory and cytotoxic effects that foster the pathogenesis of hemolytic diseases. Here, we developed and characterized a panel of heme-specific single domain antibodies (sdAbs) that together with a cellular-based heme reporter assay, allow for quantification and characterization of labile heme in plasma during hemolytic conditions. Using these approaches, we demonstrate that when generated during hemolytic conditions labile heme is bound to plasma molecules with an affinity higher than 10-7 m and that 2-8% (~ 2-5 μm) of the total amount of heme detected in plasma can be internalized by bystander cells, termed here bioavailable heme. Acute, but not chronic, hemolysis is associated with transient reduction of plasma heme-binding capacity, that is, the ability of plasma molecules to bind labile heme with an affinity higher than 10-7 m. The heme-specific sdAbs neutralize the pro-oxidant activity of soluble heme in vitro, suggesting that these maybe used to counter the pathologic effects of labile heme during hemolytic conditions. Finally, we show that heme-specific sdAbs can be used to visualize cellular heme. In conclusion, we describe a panel of heme-specific sdAbs that when used with other approaches provide novel insights to the pathophysiology of heme.

Regulation of murine cardiac contractility by activation of α1A-adrenergic receptor-operated Ca2+ entry

Abstract: Aims Sympathetic regulation of cardiac contractility is mediated in part by α1-adrenergic receptors (ARs), and the α1A-subtype has been implicated in the pathogenesis of cardiac hypertrophy. However, little is known about α1A-AR signalling pathways in ventricular myocardium. The aim of this study was to determine the signalling pathway that mediates α1A-AR-coupled cardiac contractility. Methods and results Using a transgenic model of enhanced cardiac α1A-AR expression and signalling (α1A-H mice), we identified a receptor-coupled signalling pathway that enhances Ca2+ entry and increases contractility. This pathway involves α1A-AR-activated translocation of Snapin and the transient receptor potential canonical 6 (TRPC6) channel to the plasma membrane. In ventricular cardiomyocytes from α1A-H and their non-transgenic littermates (or WTs), stimulation with α1A-AR-specific agonists resulted in increased [Ca2+]i, which was dose-related and proportional to the level of α1A-AR expression. Blockade of TRPC6 inhibited the α1A-AR-mediated increase in [Ca2+]i and contractility. External Ca2+ entry, underlying the [Ca2+]i increase, was not due to store-operated Ca2+ entry but to a receptor-operated mechanism of Ca2+ entry resulting from α1A-AR activation. Conclusion These findings indicate that Ca2+ entry via the α1A-AR-Snapin-TRPC6-pathway plays an important role in physiological regulation of cardiac contractility and may be an important target for augmenting cardiac performance.

Periconceptional Undernutrition Programs Changes in Insulin-Signaling Molecules and MicroRNAs in Skeletal Muscle in Singleton and Twin Fetal Sheep

Abstract: Maternal undernutrition around the time of conception is associated with an increased risk of insulin resistance in adulthood. We determined the effect of maternal undernutrition in the periconceptional period (PCUN, i.e., 60 days prior to 6 days after conception) and the preimplantation period (PIUN, i.e., 0–6 days after conception) on mRNA expression and protein abundance of key insulin-signaling molecules as well as the global microRNA expression in quadriceps muscle of singleton and twin fetal sheep in late gestation. In singleton fetuses, exposure to PCUN resulted in lower protein abundance of PIK3CB (P , 0.01), PRKCZ (P , 0.05), and pPRKCZ (Thr410) (P , 0.05) in skeletal muscle compared to controls. In PIUN singletons, there was a higher protein abundance of IRS1 (P , 0.05), PDPK1 (P , 0.05), and SLC2A4 (P , 0.05) compared to controls. In twins, PCUN resulted in higher protein abundance of IRS1 (P , 0.05), AKT2 (P , 0.05), PDPK1 (P , 0.05), and PRKCZ (P , 0.001), while PIUN also resulted in higher protein abundance of IRS1 (P , 0.05), PRKCZ (P , 0.001), and SLC2A4 (P , 0.05) in fetal muscle compared to controls. There were specific patterns of the types and direction of changes in the expression of 22 microRNAs in skeletal muscle after exposure to PCUN or PIUN and clear differences in these patterns between singleton and twin pregnancies. These findings provide evidence that maternal undernutrition around the time of conception induces changes in the expression of microRNAs, which may play a role in altering the abundance of the key insulin-signaling molecules in skeletal muscle and in the association between PCUN undernutrition and insulin resistance in adult life. embryo, fetus, metabolism, nutrition, oocyte