Description: Background— The cardiac cytoskeleton plays key roles in maintaining myocyte structural integrity in health and disease. In fact, human mutations in cardiac cytoskeletal elements are tightly linked to cardiac pathologies, including myopathies, aortopathies, and dystrophies. Conversely, the link between cytoskeletal protein dysfunction and cardiac electric activity is not well understood and often overlooked in the cardiac arrhythmia field. Methods and Results— Here, we uncover a new mechanism for the regulation of cardiac membrane excitability. We report that βII spectrin, an actin-associated molecule, is essential for the posttranslational targeting and localization of critical membrane proteins in heart. βII spectrin recruits ankyrin-B to the cardiac dyad, and a novel human mutation in the ankyrin-B gene disrupts the ankyrin-B/βII spectrin interaction, leading to severe human arrhythmia phenotypes. Mice lacking cardiac βII spectrin display lethal arrhythmias, aberrant electric and calcium handling phenotypes, and abnormal expression/localization of cardiac membrane proteins. Mechanistically, βII spectrin regulates the localization of cytoskeletal and plasma membrane/sarcoplasmic reticulum protein complexes, including the Na/Ca exchanger, ryanodine receptor 2, ankyrin-B, actin, and αII spectrin. Finally, we observe accelerated heart failure phenotypes in βII spectrin–deficient mice. Conclusions— Our findings identify βII spectrin as critical for normal myocyte electric activity, link this molecule to human disease, and provide new insight into the mechanisms underlying cardiac myocyte biology.

Description: Objective— The deficiency of very low-density lipoprotein receptor resulted in Wnt signaling activation and neovascularization in the retina. The present study sought to determine whether the very low-density lipoprotein receptor extracellular domain (VLN) is responsible for the inhibition of Wnt signaling in ocular tissues. Approach and Results— A plasmid expressing the soluble VLN was encapsulated with poly(lactide-co-glycolide acid) to form VLN nanoparticles (VLN-NP). Nanoparticles containing a plasmid expressing the low-density lipoprotein receptor extracellular domain nanoparticle were used as negative control. MTT, modified Boyden chamber, and Matrigel (™) assays were used to evaluate the inhibitory effect of VLN-NP on Wnt3a-stimulated endothelial cell proliferation, migration, and tube formation. Vldlr –/– mice, oxygen-induced retinopathy, and alkali burn–induced corneal neovascularization models were used to evaluate the effect of VLN-NP on ocular neovascularization. Wnt reporter mice (BAT-gal), Western blotting, and luciferase assay were used to evaluate Wnt pathway activity. Our results showed that VLN-NP specifically inhibited Wnt3a-induced endothelial cell proliferation, migration, and tube formation. Intravitreal injection of VLN-NP inhibited abnormal neovascularization in Vldlr –/– , oxygen-induced retinopathy, and alkali burn–induced corneal neovascularization models, compared with low-density lipoprotein receptor extracellular domain nanoparticle. VLN-NP significantly inhibited the phosphorylation of low-density lipoprotein receptor-related protein 6, the accumulation of β-catenin, and the expression of vascular endothelial growth factor in vivo and in vitro. Conclusions— Taken together, these results suggest that the soluble VLN is a negative regulator of the Wnt pathway and has antiangiogenic activities. Nanoparticle-mediated expression of VLN may thus represent a novel therapeutic approach to treat pathological ocular angiogenesis and potentially other vascular diseases affected by Wnt signaling.

Description: Background— Angiogenesis is crucial for many pathological processes and becomes a therapeutic strategy against diseases ranging from inflammation to cancer. The regulatory mechanism of angiogenesis remains unclear. Although tetraspanin CD82 is widely expressed in various endothelial cells (ECs), its vascular function is unknown. Methods and Results— Angiogenesis was examined in Cd82 -null mice with in vivo and ex vivo morphogenesis assays. Cellular functions, molecular interactions, and signaling were analyzed in Cd82 -null ECs. Angiogenic responses to various stimuli became markedly increased upon Cd82 ablation. Major changes in Cd82 -null ECs were enhanced migration and invasion, likely resulting from the upregulated expression of cell adhesion molecules such as CD44 and integrins at the cell surface and subsequently elevated outside-in signaling. Gangliosides, lipid raft clustering, and CD44-membrane microdomain interactions were increased in the plasma membrane of Cd82 -null ECs, leading to less clathrin-independent endocytosis and then more surface presence of CD44. Conclusions— Our study reveals that CD82 restrains pathological angiogenesis by inhibiting EC movement, that lipid raft clustering and cell adhesion molecule trafficking modulate angiogenic potential, that transmembrane protein modulates lipid rafts, and that the perturbation of CD82-ganglioside-CD44 signaling attenuates pathological angiogenesis.

Description: Background— Blood pressure (BP) responses to dietary sodium and potassium intervention and cold pressor test vary considerably among individuals. We aimed to identify novel genetic variants influencing individuals’ BP responses to dietary intervention and cold pressor test. Methods and Results— We conducted a genome-wide association study of BP responses in 1881 Han Chinese and de novo genotyped top findings in 698 Han Chinese. Diet-feeding study included a 7-day low-sodium (51.3 mmol/d), a 7-day high-sodium (307.8 mmol/d), and a 7-day high-sodium plus potassium supplementation (60 mmol/d). Nine BP measurements were obtained during baseline observation and each intervention period. The meta-analyses identified 8 novel loci for BP phenotypes, which physically mapped in or near PRMT6 ( P =7.29 x 10 –9 ), CDCA7 ( P =3.57 x 10 –8 ), PIBF1 ( P =1.78 x 10 –9 ), ARL4C ( P =1.86 x 10 –8 ), IRAK1BP1 ( P =1.44 x 10 –10 ), SALL1 ( P =7.01 x 10 –13 ), TRPM8 ( P =2.68 x 10 –8 ), and FBXL13 ( P =3.74 x 10 –9 ). There was a strong dose–response relationship between the number of risk alleles of these independent single-nucleotide polymorphisms and the risk of developing hypertension during the 7.5-year follow-up in the study participants. Compared with those in the lowest quartile of risk alleles, odds ratios (95% confidence intervals) for those in the second, third, and fourth quartiles were 1.39 (0.97, 1.99), 1.72 (1.19, 2.47), and 1.84 (1.29, 2.62), respectively ( P =0.0003 for trend). Conclusions— Our study identified 8 novel loci for BP responses to dietary sodium and potassium intervention and cold pressor test. The effect size of these novel loci on BP phenotypes is much larger than those reported by the previously published studies. Furthermore, these variants predict the risk of developing hypertension among individuals with normal BP at baseline.

Description: Background and Purpose— Total homocysteine level (tHcy) is a risk factor of ischemic stroke (IS) and coronary heart disease. However, the results are conflicting and mainly focused on healthy individuals in developed countries. Methods— A prospective, population-based cohort study was conducted among 5935 participants from 60 communities in the city of Shenzhen, China. A Cox regression analysis was applied to evaluate the contribution of tHcy to the risk of IS and coronary heart disease. The effect of folic acid supplementation on tHcy levels was also evaluated among 501 patients with essential hypertension, who received an average of 2.5 years of folic acid supplementation. Results— After adjustment for confounding factors, the hazard ratios (95% confidence intervals) of IS caused by hyperhomocysteinemia were 2.18 (1.65–2.89), 2.40 (1.56–3.67), and 2.73 (1.83–4.08) in the total, male, and female participants, respectively. Compared with normal levels of tHcy (〈15 μmol/L), the hazard ratios (95% confidence intervals) for IS in the highest tHcy category (≥30 μmol/L) were 4.96 (3.03–8.12), 6.11 (3.44–10.85), and 1.84 (0.52–6.46) in the total, males, and females participants, respectively. However, we did not observe a significant relationship between tHcy and the risk of coronary heart disease. The 2.5 years of folic acid supplementation reduced tHcy levels by 6.7 μmol/L (27.92%) in patients with essential hypertension. Conclusions— Hyperhomocysteinemia in Chinese hypertensive patients is significantly associated with IS risk but not coronary heart disease susceptibility, and folic acid supplementation can efficiently reduce tHcy levels.

Description: Background and Purpose— Soluble corin was decreased in coronary heart disease. Given the connections between cardiac dysfunction and stroke, circulating corin might be a candidate marker of stroke risk. However, the association between circulating corin and stroke has not yet been studied in humans. Here, we aimed to examine the association in patients wtith stroke and community-based healthy controls. Methods— Four hundred eighty-one patients with ischemic stroke, 116 patients with hemorrhagic stroke, and 2498 healthy controls were studied. Serum soluble corin and some conventional risk factors of stroke were examined. Because circulating corin was reported to be varied between men and women, the association between serum soluble corin and stroke was evaluated in men and women, respectively. Results— Patients with ischemic and hemorrhagic stroke had a significantly lower level of serum soluble corin than healthy controls in men and women (all P values, 〈0.05). In multivariate analysis, men in the lowest quartile of serum soluble corin were more likely to have ischemic (odds ratio [OR], 4.90; 95% confidence interval, 2.99–8.03) and hemorrhagic (OR, 17.57; 95% confidence interval, 4.85–63.71) stroke than men in the highest quartile. Women in the lowest quartile of serum soluble corin were also more likely to have ischemic (OR, 3.10; 95% confidence interval, 1.76–5.44) and hemorrhagic (OR, 8.54; 95% confidence interval, 2.35–31.02) stroke than women in the highest quartile. ORs of ischemic and hemorrhagic stroke were significantly increased with the decreasing levels of serum soluble corin in men and women (all P values for trend, 〈0.001). Conclusions— Serum soluble corin was decreased in patients with stroke compared with healthy controls. Our findings raise the possibility that serum soluble corin may have a pathogenic role in stroke.

Description: Background— Insomnia complaints are common in older adults and may be associated with mortality risk. However, evidence regarding this association is mixed. Thus, we prospectively examined whether men with insomnia symptoms had an increased risk of mortality during 6 years of follow-up. Methods and Results— A prospective cohort study of 23 447 US men participating in the Health Professionals Follow-Up Study and free of cancer, reported on insomnia symptoms in 2004, were followed through 2010. Deaths were identified from state vital statistic records, the National Death Index, family reports, and the postal system. We documented 2025 deaths during 6 years of follow-up (2004–2010). The multivariable-adjusted hazard ratios of total mortality were 1.25 (95% confidence interval [CI], 1.04–1.50) for difficulty initiating sleep, 1.09 (95% CI, 0.97–1.24) for difficulty maintaining sleep, 1.04 (95% CI, 0.88–1.22) for early-morning awakenings, and 1.24 (95% CI, 1.05–1.46) for nonrestorative sleep, comparing men with those symptoms most of the time with men without those symptoms, after adjusting for age, lifestyle factors, and presence of common chronic conditions. Men with difficulty initiating sleep and nonrestorative sleep most of the time had a 55% (hazard ratio, 1.55; 95% CI, 1.19–2.04; P -trend=0.01) and 32% (hazard ratio, 1.32; 95% CI, 1.02–1.72; P -trend=0.002) increased risk of cardiovascular disease mortality, respectively, relative to men without those symptoms. Conclusion— Some insomnia symptoms, especially difficulty initiating asleep and nonrestorative sleep, are associated with a modestly higher risk of mortality.

Description: Trimeric intracellular cation channels (TRIC) represents a novel class of trimeric intracellular cation channels. Two TRIC isoforms have been identified in both the human and the mouse genomes: TRIC-A, a subtype predominantly expressed in the sarcoplasmic reticulum (SR) of muscle cells, and TRIC-B, a ubiquitous subtype expressed in the endoplasmic reticulum (ER) of all tissues. Genetic ablation of either TRIC-A or TRIC-B leads to compromised K + permeation and Ca 2+ release across the SR/ER membrane, supporting the hypothesis that TRIC channels provide a counter balancing K + flux that reduces SR/ER membrane depolarization for maintenance of the electrochemical gradient that drives SR/ER Ca 2+ release. TRIC-A and TRIC-B seem to have differential functions in Ca 2+ signaling in excitable and nonexcitable cells. Tric-a –/– mice display defective Ca 2+ sparks and spontaneous transient outward currents in arterial smooth muscle and develop hypertension, in addition to skeletal muscle dysfunction. Knockout of TRIC-B results in abnormal IP 3 receptor–mediated Ca 2+ release in airway epithelial cells, respiratory defects, and neonatal lethality. Double knockout mice lacking both TRIC-A and TRIC-B show embryonic lethality as a result of cardiac arrest. Such an aggravated lethality indicates that TRIC-A and TRIC-B share complementary physiological functions in Ca 2+ signaling in embryonic cardiomyocytes. Tric-a –/– and Tric-b +/– mice are viable and susceptible to stress-induced heart failure. Recent evidence suggests that TRIC-A directly modulates the function of the cardiac ryanodine receptor 2 Ca 2+ release channel, which in turn controls store-overload–induced Ca 2+ release from the SR. Thus, the TRIC channels, in addition to providing a countercurrent for SR/ER Ca 2+ release, may also function as accessory proteins that directly modulate the ryanodine receptor/IP 3 receptor channel functions.