ERBB signaling attenuates proinflammatory activation of nonclassical monocytes.

Immune activation in chronic systolic heart failure (HF) correlates with disease severity and prognosis. Recombinant neuregulin-1 (rNRG-1) is being developed as a possible therapy for HF, based on the activation of ERBB receptors in cardiac cells. Work in animal models of HF led us to hypothesize that there may be direct effects of NRG-1 on immune system activation and inflammation. We investigated the expression of ERBB receptors and the effect of rNRG-1 isoform glial growth factor 2 (GGF2) in subpopulations of peripheral blood mononuclear cells (PB MNCs) in subjects with HF. We found that human monocytes express both ERBB2 and ERBB3 receptors, with high interindividual variability among subjects. Monocyte surface ERBB3 and TNF-α mRNA expression were inversely correlated in subjects with HF but not in human subjects without HF. GGF2 activation of ERBB signaling ex vivo inhibited LPS-induced TNF-α production, specifically in the CD14lowCD16+ population of monocytes in a phosphoinositide 3-kinase-dependent manner. GGF2 suppression of TNF-α correlated directly with the expression of ERBB3. In vivo, a single dose of intravenous GGF2 reduced TNF-α expression in PB MNCs of HF subjects participating in a phase I safety study of GGF2. These results support a role for ERBB3 signaling in the regulation of TNF-α production from CD14lowCD16+ monocytes and a need for further investigation into the clinical significance of NRG-1/ERBB signaling as a modulator of immune system function.NEW & NOTEWORTHY This study identified a novel role of neuregulin-1 (NRG-1)/ERBB signaling in the control of proinflammatory activation of monocytes. These results further improve our fundamental understanding of cardioprotective effects of NRG-1 in patients with heart failure.

Discoidin domain receptor 1 kinase activity is required for regulating collagen IV synthesis.

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that binds to and is activated by collagens. DDR1 expression increases following kidney injury and accumulating evidence suggests that it contributes to the progression of injury. To this end, deletion of DDR1 is beneficial in ameliorating kidney injury induced by angiotensin infusion, unilateral ureteral obstruction, or nephrotoxic nephritis. Most of the beneficial effects observed in the DDR1-null mice are attributed to reduced inflammatory cell infiltration to the site of injury, suggesting that DDR1 plays a pro-inflammatory effect. The goal of this study was to determine whether, in addition to its pro-inflammatory effect, DDR1 plays a deleterious effect in kidney injury by directly regulating extracellular matrix production. We show that DDR1-null mice have reduced deposition of glomerular collagens I and IV as well as decreased proteinuria following the partial renal ablation model of kidney injury. Using mesangial cells isolated from DDR1-null mice, we show that these cells produce significantly less collagen compared to DDR1-null cells reconstituted with wild type DDR1. Moreover, mutagenesis analysis revealed that mutations in the collagen binding site or in the kinase domain significantly reduce DDR1-mediated collagen production. Finally, we provide evidence that blocking DDR1 kinase activity with an ATP-competitive small molecule inhibitor reduces collagen production. In conclusion, our studies indicate that the kinase activity of DDR1 plays a key role in DDR1-induced collagen synthesis and suggest that blocking collagen-mediated DDR1 activation may be beneficial in fibrotic diseases.

Effects of vitamin A deficiency in the postnatal mouse heart: role of hepatic retinoid stores.

To determine whether hepatic depletion of vitamin A (VA) stores has an effect on the postnatal heart, studies were carried out with mice lacking liver retinyl ester stores fed either a VA-sufficient (LRVAS) or VA-deficient (LRVAD) diet (to deplete circulating retinol and extrahepatic stores of retinyl esters). There were no observable differences in the weights or gross morphology of hearts from LRVAS or LRVAD mice relative to sex-matched, age-matched, and genetically matched wild-type (WT) controls fed the VAS diet (WTVAS), but changes in the transcription of functionally relevant genes were consistent with a state of VAD in LRVAS and LRVAD ventricles. In silico analysis revealed that 58/67 differentially expressed transcripts identified in a microarray screen are products of genes that have DNA retinoic acid response elements. Flow cytometric analysis revealed a significant and cell-specific increase in the number of proliferating Sca-1 cardiac progenitor cells in LRVAS animals relative to WTVAS controls. Before myocardial infarction, LRVAS and WTVAS mice had similar cardiac systolic function and structure, as measured by echocardiography, but, unexpectedly, repeat echocardiography demonstrated that LRVAS mice had less adverse remodeling by 1 wk after myocardial infarction. Overall, the results demonstrate that the adult heart is responsive to retinoids, and, most notably, reducing hepatic VA stores (while maintaining circulating levels of VA) impacts ventricular gene expression profiles, progenitor cell numbers, and response to injury.

Biomimetic microstructure morphology in electrospun fiber mats is critical for maintaining healthy cardiomyocyte phenotype.

Despite recent advances in biomimetic substrates, there is still only limited understanding of how the extracellular matrix (ECM) functions in the maintenance of cardiomyocyte (CM) phenotype. In this study, we designed electrospun substrates inspired by morphologic features of non-failing and failing human heart ECM, and examined how these substrates regulate phenotypes of adult and neonatal rat ventricular CMs (ARVM and NRVM, respectively). We found that poly(ε-caprolactone) fiber substrates designed to mimic the organized ECM of a non-failing human heart maintained healthy CM phenotype (evidenced by cell morphology, organized actin/myomesin bands and expression of ß-MYH7 and SCN5A.1 and SCN5A.2) compared to both failing heart ECM-mimetic substrates and tissue culture plates. Moreover, culture of ARVMs and NRVMs on aligned substrates showed differences in m- and z-line alignment; with ARVMs aligning parallel to the ECM fibers and the NRVMs aligning perpendicular to the fibers. The results provide new insight into cardiac tissue engineering by illustrating the importance models that mimic the cardiac ECM microenvironment in vitro.

Anti-remodeling and anti-fibrotic effects of the neuregulin-1ß glial growth factor 2 in a large animal model of heart failure.

BACKGROUND: Neuregulin-1ß (NRG-1ß) is a growth factor critical for cardiac development and repair with therapeutic potential for heart failure. We previously showed that the glial growth factor 2 (GGF2) isoform of NRG-1ß improves cardiac function in rodents after myocardial infarction (MI), but its efficacy in a large animal model of cardiac injury has not been examined. We therefore sought to examine the effects of GGF2 on ventricular remodeling, cardiac function, and global transcription in post-MI swine, as well as potential mechanisms for anti-remodeling effects. METHODS AND RESULTS: MI was induced in anesthetized swine (n=23) by intracoronary balloon occlusion. At 1 week post-MI, survivors (n=13) received GGF2 treatment (intravenous, biweekly for 4 weeks; n=8) or were untreated (n=5). At 5 weeks post-MI, fractional shortening was higher (32.8% versus 25.3%, P=0.019), and left ventricular (LV) end-diastolic dimension lower (4.5 versus 5.3 cm, P=0.003) in GGF2-treated animals. Treatment altered expression of 528 genes, as measured by microarrays, including collagens, basal lamina components, and matricellular proteins. GGF2-treated pigs exhibited improvements in LV cardiomyocyte mitochondria and intercalated disk structures and showed less fibrosis, altered matrix structure, and fewer myofibroblasts (myoFbs), based on trichrome staining, electron microscopy, and immunostaining. In vitro experiments with isolated murine and rat cardiac fibroblasts demonstrate that NRG-1ß reduces myoFbs, and suppresses TGFß-induced phospho-SMAD3 as well as αSMA expression. CONCLUSIONS: These results suggest that GGF2/NRG-1ß prevents adverse remodeling after injury in part via anti-fibrotic effects in the heart.

Neuregulin-1ß induces embryonic stem cell cardiomyogenesis via ErbB3/ErbB2 receptors.

NRG-1ß (neuregulin-1ß) serves multiple functions during embryonic heart development by signalling through ErbB family receptor tyrosine kinases (ErbB2, ErbB3 and ErbB4). Previous studies reported that NRG-1ß induces cardiomyogenesis of mESCs (mouse embryonic stem cells) at the later stages of differen-tiation through ErbB4 receptor activation. In the present study we systematically examined NRG-1ß induction of cardiac myocytes in mESCs and identified a novel time window, the first 48 h, for NRG-1ß-based cardiomyogenesis. At this time point ErbB3, but not ErbB4, is expressed. In contrast with the later differentiation of mESCs in which NRG-1ß induces cardiomyogenesis via the ErbB4 receptor, we found that knocking down ErbB3 or ErbB2 with siRNA during the early differentiation inhibited NRG-1ß-induced cardiomyogenesis in mESCs. Microarray analysis of RNA expression at this early time point indicated that NRG-1ß treatment in mESCs resulted in gene expression changes important to differentiation including up-regulation of components of PI3K (phosphoinositide 3-kinase), a known mediator of the NRG-1ß/ErbB signalling pathway, as well as activation of CREB (cAMP-response-element-binding protein). Further study demonstrated that the NRG-1ß-induced phosphorylation of CREB was required for cardiomyogenesis of mESCs. In summary, we report a previously unrecognized role for NRG-1ß/ErbB3/CREB signalling at the pre-mesoderm stage for stem cell cardiac differentiation.

Psammaplysin H, a new antimalarial bromotyrosine alkaloid from a marine sponge of the genus Pseudoceratina.

Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from a marine sponge of the genus Pseudoceratina resulted in the purification of a new antimalarial bromotyrosine alkaloid, psammaplysin H (1), along with the previously isolated analogs psammaplysins G (2) and F (3). The structure of 1 was elucidated following 1D and 2D NMR, and MS data analysis. All compounds were tested in vitro against the 3D7 line of Plasmodium falciparum and mammalian cell lines (HEK293 and HepG2), with 1 having the most potent (IC(50) 0.41µM) and selective (>97-fold) antimalarial activity.

Pestalactams A-C: novel caprolactams from the endophytic fungus Pestalotiopsis sp.

Chemical investigations of a fermentation culture from the endophytic fungus Pestalotiopsis sp. yielded three novel caprolactams, pestalactams A-C (). The structures of were determined by analysis of 1D and 2D-NMR, UV, IR, and MS data. The structure of pestalactam A was confirmed following single crystal X-ray diffraction analysis. Pestalactams A-C are the first C-7 alkylated caprolactam natural products to be reported. Pestalactams A () and B () were tested against two different strains of the malaria parasite Plasmodium falciparum (3D7 and Dd2), and the mammalian cell lines, MCF-7 and NFF, and showed modest in vitro activity in all assays.