A constituent of green tea, epigallocatechin-3-gallate, activates endothelial nitric oxide synthase by a phosphatidylinositol-3-OH-kinase-, cAMP-dependent protein kinase-, and Akt-dependent pathway and leads to endothelial-dependent vasorelaxation

Epidemiological studies suggest that tea catechins may reduce the risk of cardiovascular disease, but the mechanisms of benefit have not been determined. The objective of the present study was to investigate the effects of epigallocatechin-3-gallate (EGCG), the major constituent of green tea, on vasorelaxation and on eNOS expression and activity in endothelial cells. EGCG (1-50 microm) induced dose-dependent vasodilation in rat aortic rings. Vasodilation was abolished by pretreatment with Ng-nitro L-arginine methyl ester. In bovine aortic endothelial cells, EGCG increased endothelial nitric oxide (eNOS) activity dose-dependently after 15 min. Treatment with EGCG induced a sustained activation of Akt, ERK1/2, and eNOS Ser1179 phosphorylation. Inhibition of extracellular signal-regulated kinase (ERK)1/2 had no influence on eNOS activity or Ser1179 phosphorylation. Simultaneous treatment of cells with selective inhibitors for cAMP-dependent protein kinase (PKA) and Akt completely prevented the increase in eNOS activity by EGCG after 15 min, indicating that both kinases act in concert. Specific phosphatidylinositol-3-OH-kinase inhibitors yielded identical results. Akt inhibition prevented eNOS Ser1179 phosphorylation, whereas inhibition of PKA did not influence Akt and eNOS Ser1179 phosphorylation. Pretreatment of endothelial cells with EGCG for 4 h markedly enhanced the increase in eNOS activity stimulated by Ca-ionomycin, suggesting that Akt accounts for prolonged eNOS activation. Treatment of cells for 72 h with EGCG did not change eNOS protein levels. Our results indicate that EGCG-induced endothelium-dependent vasodilation is primarily based on rapid activation of eNOS by a phosphatidylinositol 3-kinase-, PKA-, and Akt-dependent increase in eNOS activity, independently of an altered eNOS protein content.     

The causes of epistasis in genetic networks

Epistasis refers to the nonadditive interactions between genes in determining phenotypes. Considerable efforts have shown that, even for a given organism, epistasis may vary both in intensity and sign. Recent comparative studies supported that the overall sign of epistasis switches from positive to negative as the complexity of an organism increases, and it has been hypothesized that this change shall be a consequence of the underlying gene network properties. Why should this be the case? What characteristics of genetic networks determine the sign of epistasis? Here we show, by evolving genetic networks that differ in their complexity and robustness against perturbations but that perform the same tasks, that robustness increased with complexity and that epistasis was positive for small nonrobust networks but negative for large robust ones. Our results indicate that robustness and negative epistasis emerge as a consequence of the existence of redundant elements in regulatory structures of genetic networks and that the correlation between complexity and epistasis is a byproduct of such redundancy, allowing for the decoupling of epistasis from the underlying network complexity.     

Genomic deletion and promoter methylation status of Hypermethylated in Cancer 1 (HIC1) in mantle cell lymphoma

Mantle cell lymphomas (MCL), characterized by the t(11;14)(q13;q32), frequently carry secondary genetic alterations such as deletions in chromosome 17p involving the TP53 locus. Given that the association between TP53-deletions and concurrent mutations of the remaining allele is weak and based on our recent report that the Hypermethylated in Cancer 1 (HIC1) gene, that is located telomeric to the TP53 gene, may be targeted by deletions in 17p in diffuse large B-cell lymphoma (DLBCL), we investigated whether HIC1 inactivations might also occur in MCL. Monoallelic deletions of the TP53 locus were detected in 18 out of 59 MCL (31%), while overexpression of p53 protein occurred in only 8 out of 18 of these MCL (44%). In TP53-deleted MCL, the HIC1 gene locus was co-deleted in 11 out of 18 cases (61%). However, neither TP53 nor HIC1 deletions did affect survival of MCL patients. In most analyzed cases, no hypermethylation of the HIC1 exon 1A promoter was observed (17 out of 20, 85%). However, in MCL cell lines without HIC1-hypermethylation, the mRNA expression levels of HIC1 were nevertheless significantly reduced, when compared to reactive lymph node specimens, pointing to the occurrence of mechanisms other than epigenetic or genetic events for the inactivation of HIC1 in this entity.     

Experiencia con el uso del registrador implantable de eventos en una serie de personas mayores con caídas y sospecha de síncopes de origen arrítmico

Objective

To review our experience on using an implantable loop recorder (ILR) in patients with recurrent falls, when an arrhythmogenic cause is suspected.

Material and methods

This is a retrospective, observational study of patients with repetitive unexplained falls, suspected syncope, or electrocardiographic abnormalities. All of them had been evaluated by a cardiologist, who decided to implant a loop recorder (ILR) for an accurate diagnosis.

Results

A total of 13 patients received an ILR. The average falls rate for the sample was 3.3. The mean age was 78 years, and 46% were female, with a mean follow-up period of 24 months. During this time, three patients did not suffer from a new fall. An arrhythmogenic diagnosis was obtained in 5 patients: bradycardia was identified in 4 cases, and tachycardia in one of them. The symptoms did not coincide with a documented arrhythmia in the rest of the patients.

Conclusion

ILR is a helpful tool to establish an arrhythmogenic cause of unexplained and recurrent falls, in this selected sample of older adults.     

Analysis of the Role of Interleukin 6 Receptor Haplotypes in the Regulation of Circulating Levels of Inflammatory Biomarkers and Risk of Coronary Heart Disease

Variants at the interleukin 6 receptor (IL6R) gene regulate inflammation and are associated with risk of coronary heart disease (CHD). The aim of the present study was to investigate the effects of IL6R haplotypes on circulating levels of inflammatory biomarkers and risk of CHD. We performed a discovery analysis in SHEEP, a myocardial infarction (MI) case control study (n = 2,774) and replicated our results in two large, independent European populations, PROCARDIS, a CHD case control study (n = 7,998), and IMPROVE (n = 3,711) a prospective cardiovascular cohort study. Two major haplotype blocks (rs12083537A/G and rs4075015A/T—block 1; and rs8192282G/A, rs4553185T/C, rs8192284A/C, rs4240872T/C and rs7514452T/C—block 2) were identified in the IL6R gene. IL6R haplotype associations with C-reactive protein (CRP), fibrinogen, IL6, soluble IL6R (sIL6R), IL6, IL8 and TNF-α in SHEEP, CRP and fibrinogen in PROCARDIS and CRP in IMPROVE as well as association with risk of MI and CHD, were analyzed by THESIAS. Haplotypes in block 1 were associated neither with circulating inflammatory biomarkers nor with the MI/CHD risk. Haplotypes in block 2 were associated with circulating levels of CRP, in all three study populations, with fibrinogen in SHEEP and PROCARDIS, with IL8 and sIL6Rin SHEEP and with a modest, non significant, increase (7%) in MI/CHD risk in the three populations studied. Our results indicate that IL6R haplotypes regulate the circulating levels of inflammatory biomarkers. Lack of association with the risk of CHD may be explained by the combined effect of SNPs with opposite effect on the CHD risk, the sample size as well as by structural changes affecting sIL6R stability in the circulation.     

HmuS and HmuQ of <Emphasis Type="Italic">Ensifer</Emphasis>/<Emphasis Type="Italic">Sinorhizobium meliloti</Emphasis> degrade heme in vitro and participate in heme metabolism in vivo

Ensifer meliloti is a nitrogen-fixing symbiont of the alfalfa legume able to use heme as an iron source. The transport mechanism involved in heme acquisition in E. meliloti has been identified and characterized, but the fate of heme once inside the cell is not known. In silico analysis of E. meliloti 1021 genome revealed no canonical heme oxygenases although two genes encoding putative heme degrading enzymes, smc01518 and hmuS, were identified. SMc01518 is similar to HmuQ of Bradyrhizobium japonicum, which is weakly homologous to the Staphylococcus aureus IsdG heme-degrading monooxygenase, whereas HmuS is homolog to Pseudomonas aeruginosa PhuS, a protein reported as a heme chaperone and as a heme degrading enzyme. Recombinant HmuQ and HmuS were able to bind hemin with a 1:1 stoichiometry and displayed a K_d value of 5 and 4 µM, respectively. HmuS degrades heme in vitro to the biliverdin isomers IX-β and IX-δ in an equimolar ratio. The HmuQ recombinant protein degrades heme to biliverdin IX-δ only. Additionally, in this work we demonstrate that humS and hmuQ gene expression is regulated by iron and heme in a RirA dependent manner and that both proteins are involved in heme metabolism in E. meliloti in vivo.