Comment on Neiser et al. Assessment of Dextran Antigenicity of Intravenous Iron Preparations with Enzyme-Linked Immunosorbent Assay (ELISA). Int. J. Mol. Sci. 2016, 17, 1185.

All IV iron complexes carry a risk of potentially fatal allergic type hypersensitivity reactions. The mechanism(s) behind these reactions is unknown but the limited data available suggests that classic IgE mediated allergy is exceedingly rare, if ever occurring. Iron-carbohydrate molecules are complex nano-particles and trying to reduce the risk of serious hypersensitivity to antibody binding of an artificial antibody seems meaningless. A recently published analysis of safety data from randomized clinical trials confirms the method reported by Neiser to be useless to predict reaction risk. In conclusion, the study by Neiser et al. is biased, contains no new information, and has no clinical relevance. We are concerned that the association of the authors with a commercial entity has caused a conflict of interest that biases not only the results, but the entire experimental setup against competitors. (Comment on Neiser et al. Int. J. Mol. Sci. 2016, 17, 1185, doi:10.3390/ijms17071185).

S100A4 is upregulated in injured myocardium and promotes growth and survival of cardiac myocytes.

OBJECTIVE: The multifunctional Ca2+-binding protein S100A4 (also known as Mts1 and Fsp1) is involved in fibrosis and tissue remodeling in several diseases including cancer, kidney fibrosis, central nervous system injury, and pulmonary vascular disease. We previously reported that S100A4 mRNA expression was increased in hypertrophic rat hearts and that it has pro-cardiomyogenic effects in embryonic stem cell-derived embryoid bodies. We therefore hypothesized that S100A4 could play a supportive role in the injured heart. METHODS AND RESULTS: Here we verify by quantitative real-time PCR and immunoblotting that S100A4 mRNA and protein is upregulated in hypertrophic rat and human hearts and show by way of confocal microscopy that S100A4 protein, but not mRNA, appears in cardiac myocytes only in the border zone after an acute ischemic event in rat and human hearts. In normal rat and human hearts, S100A4 expression primarily colocalizes with markers of fibroblasts. In hypertrophy elicited by aortic banding/stenosis or myocardial infarction, this expression is increased. Moreover, invading macrophages and leucocytes stain strongly for S100A4, further increasing cardiac levels of S100A4 protein after injury. Promisingly, recombinant S100A4 protein elicited a robust hypertrophic response and increased the number of viable cells in cardiac myocyte cultures by inhibiting apoptosis. We also found that ERK1/2 activation was necessary for both the hypertrophy and survival effects of S100A4 in vitro. CONCLUSIONS: Along with proposed angiogenic and cell motility stimulating effects of S100A4, these findings suggest that S100A4 can act as a novel cardiac growth and survival factor and may have regenerative effects in injured myocardium.

Expression profiling reveals differences in metabolic gene expression between exercise-induced cardiac effects and maladaptive cardiac hypertrophy.

While cardiac hypertrophy elicited by pathological stimuli eventually leads to cardiac dysfunction, exercise-induced hypertrophy does not. This suggests that a beneficial hypertrophic phenotype exists. In search of an underlying molecular substrate we used microarray technology to identify cardiac gene expression in response to exercise. Rats exercised for seven weeks on a treadmill were characterized by invasive blood pressure measurements and echocardiography. RNA was isolated from the left ventricle and analysed on DNA microarrays containing 8740 genes. Selected genes were analysed by quantitative PCR. The exercise program resulted in cardiac hypertrophy without impaired cardiac function. Principal component analysis identified an exercise-induced change in gene expression that was distinct from the program observed in maladaptive hypertrophy. Statistical analysis identified 267 upregulated genes and 62 downregulated genes in response to exercise. Expression changes in genes encoding extracellular matrix proteins, cytoskeletal elements, signalling factors and ribosomal proteins mimicked changes previously described in maladaptive hypertrophy. Our most striking observation was that expression changes of genes involved in beta-oxidation of fatty acids and glucose metabolism differentiate adaptive from maladaptive hypertrophy. Direct comparison to maladaptive hypertrophy was enabled by quantitative PCR of key metabolic enzymes including uncoupling protein 2 (UCP2) and fatty acid translocase (CD36). DNA microarray analysis of gene expression changes in exercise-induced cardiac hypertrophy suggests that a set of genes involved in fatty acid and glucose metabolism could be fundamental to the beneficial phenotype of exercise-induced hypertrophy, as these changes are absent or reversed in maladaptive hypertrophy.

Involvement of cyclin D activity in left ventricle hypertrophy in vivo and in vitro.

OBJECTIVE: Cardiac hypertrophy is induced by a number of stimuli and can lead to cardiomyopathy and heart failure. Present knowledge suggests that cell-cycle regulatory proteins take part in hypertrophy. We have investigated if the D-type cyclins are involved in cardiac hypertrophy. METHODS: The expression and activity of the D-type cyclins and associated kinases in cardiomyocytes were studied during angiotensin II- and pressure overload-induced hypertrophy in rats (Rattus norvegicus) and in isolated, neonatal cardiomyocytes. Expression of the D-type cyclins was manipulated pharmacologically and genetically in neonatal myocytes. RESULTS: In the left ventricle, there was a low, constitutive expression of the D-type cyclins, which may have a biological role in normal, adult myocytes. The protein level and the associated kinase activity of the D-type cyclins were up-regulated during hypertrophic growth. The increase in cyclin D expression could be mimicked in vitro in neonatal cardiac myocytes. Interestingly, the cyclin Ds were up-regulated by hypertrophic elicitors that stimulate different signalling pathways, suggesting that cyclin D expression is an inherent part of cardiac hypertrophy. Treatment of myocytes with the compound differentiation inducing factor 1 inhibited expression of the D-type cyclins and impaired hypertrophic growth induced by angiotensin II, phenylephrine and serum. The response to hypertrophic elicitors could be restored in differentiation inducing factor 1-treated myocytes by expressing cyclin D2 from a heterologous promoter. CONCLUSION: Our results point to the D-type cyclins as important regulators of cardiac hypertrophy. This supports the notion that cell-cycle regulatory proteins regulate hypertrophic growth.

Increased natriuretic peptide receptor A and C gene expression in rats with pressure-overload cardiac hypertrophy.

Both atrial (ANP) and brain (BNP) natriuretic peptide affect development of cardiac hypertrophy and fibrosis via binding to natriuretic peptide receptor (NPR)-A in the heart. A putative clearance receptor, NPR-C, is believed to regulate cardiac levels of ANP and BNP. The renin-angiotensin system also affects cardiac hypertrophy and fibrosis. In this study we examined the expression of genes for the NPRs in rats with pressure-overload cardiac hypertrophy. The ANG II type 1 receptor was blocked with losartan (10 mg.kg(-1).day(-1)) to investigate a possible role of the renin-angiotensin system in regulation of natriuretic peptide and NPR gene expression. The ascending aorta was banded in 84 rats during Hypnorm/Dormicum-isoflurane anesthesia; after 4 wk the rats were randomized to treatment with losartan or placebo. The left ventricle of the heart was removed 1, 2, or 4 wk later. Aortic banding increased left ventricular expression of NPR-A and NPR-C mRNA by 110% (P < 0.001) and 520% (P < 0.01), respectively, after 8 wk; as expected, it also increased the expression of ANP and BNP mRNAs. Losartan induced a slight reduction of left ventricular weight but did not affect the expression of mRNAs for the natriuretic peptides or their receptors. Although increased gene expression does not necessarily convey a higher concentration of the protein, the data suggest that pressure overload is accompanied by upregulation of not only ANP and BNP but also their receptors NPR-A and NPR-C in the left ventricle.

Multiprotein bridging factor 1 cooperates with c-Jun and is necessary for cardiac hypertrophy in vitro.

Cardiac hypertrophy is induced by a number of stimuli and can lead to cardiomyopathy and heart failure. Cardiomyocyte hypertrophy is characterized by increased cell size and altered gene expression. By differential-display polymerase chain reaction and Western blotting we found that the transcriptional coactivator MBF1 was upregulated during hypertrophy in cardiomyocyte cultures. Furthermore, MBF1 protein level increased in two animal models of hypertrophy, angiotensin II treatment and aortic banding. MBF1 antisense oligodeoxynuclotides blocked phenylephrine-induced hypertrophy, suggesting MBF1 plays a key role in hypertrophic growth. In contrast, overexpression of MBF1 potentiated the hormone-induced response of the atrial natriuretic peptide promoter. MBF1 overexpressed by transient transfection cooperated with the transcription factor c-Jun in activation of transcription but not with GATA4. MBF1 and c-Jun induced the activity of a transiently transfected atrial natriuretic peptide promoter, whereas neither MBF1 nor c-Jun could induce the promoter alone. Moreover, MBF1 bound to c-Jun in vitro. These data suggest that MBF1 is a transcriptional coactivator of c-Jun regulating hypertrophic gene expression. Inhibitor studies suggested that MBF1 activates the atrial natriuretic peptide promoter independently of the calcineurin and CaMK signaling pathways. Our results indicate that MBF1 participates in hormone-induced cardiomyocyte hypertrophy and activates hypertrophic gene expression as a coactivator of c-Jun.

Identification of a core set of genes that signifies pathways underlying cardiac hypertrophy.

Although the molecular signals underlying cardiac hypertrophy have been the subject of intense investigation, the extent of common and distinct gene regulation between different forms of cardiac hypertrophy remains unclear. We hypothesized that a general and comparative analysis of hypertrophic gene expression, using microarray technology in multiple models of cardiac hypertrophy, including aortic banding, myocardial infarction, an arteriovenous shunt and pharmacologically induced hypertrophy, would uncover networks of conserved hypertrophy-specific genes and identify novel genes involved in hypertrophic signalling. From gene expression analyses (8740 probe sets, n = 46) of rat ventricular RNA, we identified a core set of 139 genes with consistent differential expression in all hypertrophy models as compared to their controls, including 78 genes not previously associated with hypertrophy and 61 genes whose altered expression had previously been reported. We identified a single common gene program underlying hypertrophic remodelling, regardless of how the hypertrophy was induced. These genes constitute the molecular basis for the existence of one main form of cardiac hypertrophy and may be useful for prediction of a common therapeutic approach. Supplementary material for this article can be found at: http://www.interscience.wiley.com/jpages/1531-6912/suppmat.