心源性猝死心电预测和综合防治研究进展

随着社会老龄化的进一步加剧,冠心痛、高血压、心肌病、恶性心律失常的发病率也成为导致人群中猝死率上升的重要诱发因素.对猝死发病机制的研究中,室性心动过速和室颤往往是导致病人发生猝死的最主要的终末事件.在这篇文章中我们通过12导联心电图(ECG)的心电学预测因子的研究,揭示心电学预测因子在预防心源性猝死中的临床应用价值.另一方面,如何能提高预防猝死的预测因子的敏感性和特异性,发现新的更有临床应用价值的心电学预测因子,更好的防治猝死对社会人群的危害,成为临床研究中不断探寻的答案.最后,我们将近年来对心源性猝死的防治措施及未来的发展方向做一简要的综述.     

Vitreous TIMP-1 levels associate with neovascularization and TGF-β2 levels but not with fibrosis in the clinical course of proliferative diabetic retinopathy

In proliferative diabetic retinopathy (PDR), vascular endothelial growth factor (VEGF) and CCN2 (connective tissue growth factor; CTGF) cause blindness by neovascularization and subsequent fibrosis. This angio-fibrotic switch is associated with a shift in the balance between vitreous levels of CCN2 and VEGF in the eye. Here, we investigated the possible involvement of other important mediators of fibrosis, tissue inhibitor of metalloproteinases (TIMP)-1 and transforming growth factor (TGF)-β2, and of the matrix metalloproteinases (MMP)-2 and MMP-9, in the natural course of PDR. TIMP-1, activated TGF-β2, CCN2 and VEGF levels were measured by ELISA in 78 vitreous samples of patients with PDR (n = 28), diabetic patients without PDR (n = 24), and patients with the diabetes-unrelated retinal conditions macular hole (n = 10) or macular pucker (n = 16), and were related to MMP-2 and MMP-9 activity on zymograms and to clinical data, including degree of intra-ocular neovascularization and fibrosis. TIMP-1, CCN2 and VEGF levels, but not activated TGF-β2 levels, were significantly increased in the vitreous of diabetic patients, with the highest levels in PDR patients. CCN2 and the CCN2/VEGF ratio were the strongest predictors of degree of fibrosis. In diabetic patients with or without PDR, activated TGF-β2 levels correlated with TIMP-1 levels, whereas in PDR patients, TIMP-1 levels, MMP-2 and proMMP-9 were associated with degree of neovascularization, like VEGF levels, but not with fibrosis. We confirm here our previous findings that retinal fibrosis in PDR patients is significantly correlated with vitreous CCN2 levels and the CCN2/VEGF ratio. In contrast, TIMP-1, MMP-2 and MMP-9 appear to have a role in the angiogenic phase rather than in the fibrotic phase of PDR.     

NLRP3 inflammasome negatively regulates podocyte autophagy in diabetic nephropathy

Inflammasome mechanisms are recognized as a key pathophysiology of diabetic nephropathy (DN). The nucleotide-oligomerization domain-like receptor 3 (NLRP3) inflammasome has attracted the most attention. Autophagy as a conserved intracellular catabolic pathway plays essential roles in the maintenance of podocytes. Although autophagy was involved in preventing excessive inflammatory responses in kidney diseases, a clear understanding of the regulation of NLRP3 inflammasome on autophagy in glomerular damage in DN is still lacking. In this study, we focused on the effect of the activation of NLRP3 inflammasome on the suppression of podocyte autophagy and aimed to investigate the role of autophagy in podocyte injury in DN. Podocyte autophagy has been confirmed to be inhibited in high-fat diet/streptozotocin (HFD/STZ)-induced DN mice, and NLRP3 has been found to be upregulated in both mice and human DN biopsies and in vitro. Activation of NLRP3 inflammasome exacerbated podocyte autophagy and reduced podocyte nephrin expression, while silencing of NLRP3 efficiently restored podocyte autophagy and ameliorated podocyte injury induced by high glucose. The results showed that NLRP3 was a negative regulator of autophagy and suggested that restoration of podocyte autophagy by inactivation of NLRP3 under high glucose could reduce podocyte injury. Proper modification of autophagy and inflammasome has the potential to benefit the kidney in DN.     

M8R tropomyosin mutation disrupts actin binding and filament regulation: The beginning affects the middle and end

Dilated cardiomyopathy (DCM) is associated with mutations in cardiomyocyte sarcomeric proteins, including α-tropomyosin. In conjunction with troponin, tropomyosin shifts to regulate actomyosin interactions. Tropomyosin molecules overlap via tropomyosin–tropomyosin head-to-tail associations, forming a continuous strand along the thin filament. These associations are critical for propagation of tropomyosin''s reconfiguration along the thin filament and key for the cooperative switching between heart muscle contraction and relaxation. Here, we tested perturbations in tropomyosin structure, biochemistry, and function caused by the DCM-linked mutation, M8R, which is located at the overlap junction. Localized and nonlocalized structural effects of the mutation were found in tropomyosin that ultimately perturb its thin filament regulatory function. Comparison of mutant and WT α-tropomyosin was carried out using in vitro motility assays, CD, actin co-sedimentation, and molecular dynamics simulations. Regulated thin filament velocity measurements showed that the presence of M8R tropomyosin decreased calcium sensitivity and thin filament cooperativity. The co-sedimentation of actin and tropomyosin showed weakening of actin-mutant tropomyosin binding. The binding of troponin T''s N terminus to the actin-mutant tropomyosin complex was also weakened. CD and molecular dynamics indicate that the M8R mutation disrupts the four-helix bundle at the head-to-tail junction, leading to weaker tropomyosin–tropomyosin binding and weaker tropomyosin–actin binding. Molecular dynamics revealed that altered end-to-end bond formation has effects extending toward the central region of the tropomyosin molecule, which alter the azimuthal position of tropomyosin, likely disrupting the mutant thin filament response to calcium. These results demonstrate that mutation-induced alterations in tropomyosin–thin filament interactions underlie the altered regulatory phenotype and ultimately the pathogenesis of DCM.     

Functional characterization of human myosin-binding protein C3 variants associated with hypertrophic cardiomyopathy reveals exon-specific cardiac phenotypes in zebrafish model

Myosin-binding protein C 3 (MYBPC3) variants are the most common cause of hypertrophic cardiomyopathy (HCM). HCM is a complex cardiac disorder due to its significant genetic and clinical heterogeneity. MYBPC3 variants genotype–phenotype associations remain poorly understood. We investigated the impact of two novel human MYBPC3 splice-site variants: V1: c.654+2_654+4dupTGG targeting exon 5 using morpholino MOe5i5; and V2: c.772+1G>A targeting exon 6 using MOe6i6; located within C1 domain of cMyBP-C protein, known to be critical in regulating sarcomere structure and contractility. Zebrafish MOe5i5 and MOe6i6 morphants recapitulated typical characteristics of human HCM with cardiac phenotypes of varying severity, including reduced cardiomyocyte count, thickened ventricular myocardial wall, a drastic reduction in heart rate, stroke volume, and cardiac output. Analysis of all cardiac morphological and functional parameters demonstrated that V2 cardiac phenotype was more severe than V1. Coinjection with synthetic human MYBPC3 messenger RNA (mRNA) partially rescued disparate cardiac phenotypes in each zebrafish morphant. While human MYBPC3 mRNA partially restored the decreased heart rate in V1 morphants and displayed increased percentages of ejection fraction, fractional shortening, and area change, it failed to revert the V1 ventricular myocardial thickness. These results suggest a possible V1 impact on cardiac contractility. In contrast, attempts to rescue V2 morphants only restored the ventricular myocardial wall hypertrophy phenotype but had no significant effect on impaired heart rate, suggesting a potential V2 impact on the cardiac structure. Our study provides evidence of an association between MYBPC3 exon-specific cardiac phenotypes in the zebrafish model providing important insights into how these genetic variants contribute to HCM disease.     

miR-222 inhibits cardiac fibrosis in diabetic mice heart via regulating Wnt/β-catenin-mediated endothelium to mesenchymal transition

miR-222 participates in many cardiovascular diseases, but its effect on cardiac remodeling induced by diabetes is unclear. This study evaluated the functional role of miR-222 in cardiac fibrosis in diabetic mice. Streptozotocin (STZ) was used to establish a type 1 diabetic mouse model. After 10 weeks of STZ injection, mice were intravenously injected with Ad-miR-222 to induce the overexpression of miR-222. miR-222 overexpression reduced cardiac fibrosis and improved cardiac function in diabetic mice. Mechanistically, miR-222 inhibited the endothelium to mesenchymal transition (EndMT) in diabetic mouse hearts. Mouse heart fibroblasts and endothelial cells were isolated and cultured with high glucose (HG). An miR-222 mimic did not affect HG-induced fibroblast activation and function but did suppress the HG-induced EndMT process. The antagonism of miR-222 by antagomir inhibited HG-induced EndMT. miR-222 regulated the promoter region of β-catenin, thus negatively regulating the Wnt/β-catenin pathway, which was confirmed by β-catenin siRNA. Taken together, our results indicated that miR-222 inhibited cardiac fibrosis in diabetic mice via negatively regulating Wnt/β-catenin-mediated EndMT.     

Cardiomyocyte-specific perilipin 5 overexpression leads to myocardial steatosis and modest cardiac dysfunction

Presence of ectopic lipid droplets (LDs) in cardiac muscle is associated to lipotoxicity and tissue dysfunction. However, presence of LDs in heart is also observed in physiological conditions, such as when cellular energy needs and energy production from mitochondria fatty acid β-oxidation are high (fasting). This suggests that development of tissue lipotoxicity and dysfunction is not simply due to the presence of LDs in cardiac muscle but due at least in part to alterations in LD function. To examine the function of cardiac LDs, we obtained transgenic mice with heart-specific perilipin 5 (Plin5) overexpression (MHC-Plin5), a member of the perilipin protein family. Hearts from MHC-Plin5 mice expressed at least 4-fold higher levels of plin5 and exhibited a 3.5-fold increase in triglyceride content versus nontransgenic littermates. Chronic cardiac excess of LDs was found to result in mild heart dysfunction with decreased expression of peroxisome proliferator-activated receptor (PPAR)α target genes, decreased mitochondria function, and left ventricular concentric hypertrophia. Lack of more severe heart function complications may have been prevented by a strong increased expression of oxidative-induced genes via NF-E2-related factor 2 antioxidative pathway. Perilipin 5 regulates the formation and stabilization of cardiac LDs, and it promotes cardiac steatosis without major heart function impairment.     

Computational Investigation of Pkcβ Inhibitors for the Treatment of Diabetic Retinopathy

Diabetic Retinopathy (DR) is one of the attenuating complications of diabetes mellitus. The key gene responsible for causing diabetic retinopathy is protein kinase C beta (PKCβ). Protein kinase C is a family of protein kinase enzymes which are involved in controlling the function of other proteins through phosphorylation mechanism and plays a crucial role in signal transduction mechanisms. Among all the PKC isoenzymes, PKCβ could be a significant isoenzyme involved in vascular dysfunction during hyperglycemia. Studies show that oral administration of PKCβ inhibitor Ruboxistaurin ({"type":"entrez-nucleotide","attrs":{"text":"LY333531","term_id":"1257370768","term_text":"LY333531"}}LY333531), decreases vessel permeability and improves retinal condition. Thus compounds that decrease the PKCβ activation would be helpful in the treatment of diabetic retinopathy. The compounds similar to Ruboxistaurin are taken from Super Target database and docking analysis was performed. Maleimide derivative 3 showed highest binding affinities compared to Ruboxistaurin and so we advise that compound may be utilized in the treatment of diabetic retinopathy.