A novel approach for developing left bundle branch pacing and left bundle branch block in a canine model.

BACKGROUND AND OBJECTIVE: Left bundle branch pacing (LBBP) has shown the benefits in the treatment of dyssynchronous heart failure (HF). The purpose of this study was to develop a novel approach for LBBP and left bundle branch block (LBBB) in a canine model. METHODS: A "triangle-center" method by tricuspid valve annulus angiography for LBBP implantation was performed in 6 canines. A catheter was then applied for retrograde His potential recording and left bundle branch (LBB) ablation simultaneously. The conduction system was stained to verify the "triangle-center" method for LBBP and assess the locations of the LBB ablation site in relation to the left septal fascicle (LSF). RESULTS: The mean LBB potential to ventricular interval and stimulus-peak left ventricular activation time were 11.8 ± 1.2 and 35.7 ± 3.1 ms, respectively. The average intrinsic QRS duration was 44.7 ± 4.7 ms. LBB ablation significantly prolonged the QRS duration (106.3 ± 8.3 ms, p < .001) while LBBP significantly shortened the LBBB-QRS duration to 62.5 ± 5.3 ms (p < .001). After 6 weeks of follow-up, both paced QRS duration (63.0 ± 5.4 ms; p = .203) and LBBB-QRS duration (107.3 ± 7.4 ms; p = .144) were unchanged when comparing to the acute phase, respectively. Anatomical analysis of 6 canine hearts showed that the LBBP lead-tip was all placed in LSF area. CONCLUSION: The new approach for LBBP and LBBB canine model was stable and feasible to simulate the clinical dyssynchrony and resynchronization. It provided a useful tool to investigate the basic mechanisms of underlying physiological pacing benefits.

The mediation function of resting heart rate in how physical activity improves all-cause mortality: Continuous and automatic measurement via cardiac implantable electronic devices.

Background: Physical activity (PA) and resting heart rate (RHR) are connected with all-cause mortality. Moreover, there was an inverse correlation between PA and RHR. However, the causal relationship between PA, RHR, and long-term mortality has been rarely evaluated and quantified, particularly the mediation effect of RHR in the association between PA and all-cause mortality. Objective: To describe the relationship between PA and RHR when consistently measured via cardiac implantable electronic devices (CIED) and further explore the mediation effect of PA on all-cause mortality through RHR. Materials and methods: Patients who underwent CIED implantation and received remote home monitoring services were included. During the first 30-60 days after CIED implantation, daily PA and RHR were continuously measured and automatically transmitted by CIED. The primary endpoint was all-cause mortality. The multiple linear regression model was used to confirm the relationship between PA and RHR. The predictive values of both PA and RHR for all-cause mortality were assessed by multivariable Cox proportional hazards models. The causal mediation model was further established to verify and quantify the mediation effect of RHR in the association between PA and all-cause mortality. Results: A total of 730 patients with CIED were included. The mean daily PA and RHR were 10.7 ± 5.7% and 61.3 ± 9.1 bpm, respectively. During a mean follow-up period of 55.8 months, 187 (26.5%) death was observed. A negative linear relationship between PA and RHR was demonstrated in the multiple regression model (ß = -0.260; 95% CI: -0.377 to -0.143, p < 0.001). Multivariable Cox proportional hazards analysis showed that both lower levels of PA (HR = 0.907; 95% CI: 0.878-0.936, p < 0.001) and higher RHR (HR = 1.016; 95% CI: 1.001-1.032, P = 0.031) were independent risk factors of all-cause mortality. Causal mediation analysis further confirmed and quantified the mediation function of RHR in the process of PA improving all-cause mortality (mediation proportion = 3.9%; 95% CI: 0.2-10.0%, p = 0.036). Conclusion: The effects of the higher level of PA on improving life prognosis may be partially mediated through RHR among patients with CIED. It indicates that changes in the autonomic nervous function during postoperative rehabilitation exercises should get more attention.

Association of time-varying changes in physical activity with cardiac death and all-cause mortality after ICD or CRT-D implantation.

OBJECTIVE: To evaluate the association of longitudinal changes in physical activity (PA) with long-term outcomes after implantable cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D) implantation. METHODS: Patients with ICD/CRT-D implantation from SUMMIT registry were retrospectively analyzed. Accelerometer-derived PA changes over 12 months post implantation were obtained from the archived home monitoring data. The primary endpoints were cardiac death and all-cause mortality. The secondary endpoints were the first ventricular arrthymia (VA) and first appropriate ICD shock. RESULTS: In 705 patients, 446 (63.3%) patients showed improved PA over 12 months after implantation. During a mean 61.5-month follow-up duration, 99 cardiac deaths (14.0%) and 153 all-cause deaths (21.7%) occurred. Compared to reduced/unchanged PA, improved PA over 12 months could result in significantly reduced risks of cardiac death (improved PA ≤ 30 min: hazard ratio (HR) = 0.494, 95% CI: 0.288-0.848; > 30 min: HR = 0.390, 95% CI: 0.235-0.648) and all-cause mortality (improved PA ≤ 30 min: HR = 0.467, 95%CI: 0.299-0.728; > 30 min: HR = 0.451, 95% CI: 0.304-0.669). No differences in the VAs or ICD shocks were observed across different groups of PA changes. PA changes can predict the risks of cardiac death only in the low baseline PA group, but improved PA was associated with 56.7%, 57.4%, and 62.3% reduced risks of all-cause mortality in the low, moderate, and high baseline PA groups, respectively, than reduced/unchanged PA. CONCLUSIONS: Improved PA could protect aganist cardiac death and all-cause mortality, probably reflecting better clinical efficacy after ICD/CRT-D implantation. Low-intensity exercise training might be encouraged among patients with different baseline PA levels.

Low-Dose Ibutilide Combined with Catheter Ablation of Persistent Atrial Fibrillation: Procedural Impact and Clinical Outcome.

BACKGROUND: In patients with persistent atrial fibrillation (AF), the procedural and clinical outcomes of ablation combined with infusion of antiarrhythmic drug are unknown. OBJECTIVES: To determine the impact of low-dose ibutilide after circumferential pulmonary vein isolation (CPVI) and/or left atrial (LA) substrate modification on acute procedural and clinical outcome of persistent AF. METHODS: In a prospective cohort of 135 consecutive patients with persistent AF, intravenous 0.25 mg ibutilide was administered 3 days before the procedure and intraprocedurally, if required, after CPVI and/or additional LA substrate modification of sites with continuous, rapid or fractionated, and low-voltage (0.05-0.3 mv) atrial activity. RESULTS: Persistent AF was terminated by CPVI alone (n=15) or CPVI + ibutilide (n=32) in 47 (34.8%) patients (CPVI responders). Additional LA substrate modification without (n=33) or with subsequent administration of 0.25 mg ibutilide (n=19) terminated AF in another 52 (38.5%) patients (substrate modification responders). Sinus rhythm was restored by electrical cardioversion in the remaining 36 (26.7%) patients (nonresponders). The mean LA substrate ablation time was 14 ± 6 minutes. At follow-up of 24 ± 10 months, the rates of freedom from atrial tachyarrhythmias among the responders in CPVI and substrate modification groups were mutually comparable (66.0% and 69.2%) and higher than among the nonresponders (36.1%; P < 0.01). Among the responders, there was no difference in clinical outcome between patients whose persistent AF was terminated without or with low-dose ibutilide. CONCLUSION: Administration of low-dose ibutilide during ablation of persistent AF may allow select patients wherein substrate ablation is not or minimally required to optimize procedural and clinical outcomes.

Radiofrequency Catheter Ablation Versus Cryoballoon Ablation in the Treatment of Paroxysmal Atrial Fibrillation: A Cost-effectiveness Analysis in China.

PURPOSE: The aim of this study was to evaluate the cost-effectiveness of radiofrequency catheter ablation (RFCA) compared with cryoballoon (CB) ablation in the treatment of patients with paroxysmal atrial fibrillation (PAF) from the payer's perspective in China. METHODS: We constructed a cohort model, combining a 12-month decision-tree model with a lifetime Markov state-transition model, in a hypothetical cohort of patients with drug-refractory PAF managed with either RFCA or CB ablation, to compare the cost-effectiveness of the 2 procedures. Data related to clinical outcomes and costs in this model were obtained from a retrospective 12-month follow-up study in patients in China and from related literature. The incremental cost-effectiveness ratio (ICER) over a 10-year time period was calculated and compared against the willingness-to-pay (WTP) threshold. We used a 1-way sensitivity analysis and a probabilistic sensitivity analysis (PSA) to access the structural uncertainty and the parameter uncertainty, respectively. FINDINGS: Over a 10-year time horizon, the total costs per patient of RFCA and CB ablation were ¥98,164.04 (US $15,339.57; €13,058.94) and ¥107,542.37 ($16,805.07; €14,306.55), respectively, and quality-adjusted life-years (QALYs) gained were 5.47 and 5.43, respectively. The ICER ratio was -¥224,365.01 (-$35,060.32; -€29,847.68) per QALY, indicating that RFCA is associated with greater QALYs and lower costs than CB ablation. The 1-way sensitivity analysis demonstrated that the model results were most sensitive to the odds ratio of the atrial fibrillation recurrence within 12 months in the RFCA group versus the CB ablation group, the cost of RFCA, and the perioperative stroke risk with RFCA. According to the results of the PSA, RFCA was associated with a high probability of being cost-effective (99.48%) compared with CB ablation at a WTP threshold of ¥161,940 ($25,305.50; €21,543.17) per QALY. IMPLICATIONS: Our analysis indicates that RFCA is cost-saving compared with CB ablation in the treatment of patients with PAF in China, based on better QALYs and lower costs over a 10-year time horizon, from the payer's perspective.

PMT1 deficiency extends the shortened replicative lifespan of TED1-deficient yeast in a Hac1p-dependent manner.

Protein O-mannosyltransferase-1 (Pmt1p) deficiency extends the replicative lifespan (RLS) of Saccharomyces cerevisiae, which is related to the activation of the unfolded protein response (UPR), an important pathway for alleviating endoplasmic reticulum (ER) stress. Trafficking of Emp24p/Erv25p-dependent cargo disrupted 1 (Ted1p) has been reported as a binding partner of yeast Pmt1p. We explored the potential relationship between Pmt1p and Ted1p in the cell lifespan and ER stress responses. The TED1-deleted strain (ted1Δ) had a shorter RLS with no increase in UPR activity. However, PMT1 deficiency prolonged the short lifespan of ted1Δ in a manner dependent on Hac1p, an upstream transcription factor of the UPR pathway. In addition, PMT1 deficiency enhanced the UPR activity and alleviated the ER stress resistance of the ted1Δ strain. Thus, the enhanced UPR activity was hypothesized to explain the longevity of the pmt1Δted1Δ strain, but this long-lived pmt1Δted1Δ strain showed decreased ER stress resistance compared with the short-lived ted1Δ strain. Taken together, our results suggest a possible relationship between PMT1 and TED1 regarding lifespan regulation and the ER stress response.

Amyloid beta deposition related retinal pigment epithelium cell impairment and subretinal microglia activation in aged APPswePS1 transgenic mice.

AIM: To identify the pathological role of amyloid beta (Aß) deposition in retinal degeneration, and explore Aß deposition on the retinal pigment epithelium cells (RPE) layer and the associated structural and functional changes in Alzheimer's disease transgenic mice. METHODS: RPE changes in the eyes of APPswe/PS1 transgenic and none transgenic (NTG) mice over 20 months old were examined. Histological changes were investigated via hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM) examination, whereas the expression of amyloid precursor protein (APP), Aß, Zonula occludens-1 (ZO-1) and Ionized calcium binding adaptor molecule-1 (IBA-1) were investigated using immunohistochemistry and immunofluorescence techniques. All of the obtained results were quantitatively and statistically analyzed. RESULTS: In aged transgenic mice, an APP-positive immunoreaction and Aß deposition were detected on the RPE layer but were undetectable in NTG mice. The RPE demonstrated some vacuole changes, shortened basal infoldings and basal deposition in histopathological examination and TEM tests, wherein irregular shapes were indicated by ZO-1 disorganization through fluorescence. Furthermore, IBA-1 positive cells were observed to have accumulated and infiltrated into the RPE layer and localized beneath the RPE/Bruch's membrane (BrM) complex, which was accompanied by an increase in BrM thickness in aged transgenic mice in comparison to NTG mice. The IBA-1 positive cells were found to be co-stained with Aß deposition on the RPE flat mounts. CONCLUSION: The observed Aß deposition in the RPE layer may cause RPE dysfunction, which is associated with microglia cells infiltration into the retina of aged transgenic mice, suggesting that Aß deposition probably plays a significant role in RPE-related degenerative disease.

Effects of Astaxanthin on Reverse Cholesterol Transport and Atherosclerosis in Mice.

High plasma level of HDL-cholesterol (HDL-C) has been consistently associated with a decreased risk of atherosclerosis (AS); thus, HDL-C is considered to be an antiatherogenic lipoprotein. The development of novel therapies to enhance the atheroprotective properties of HDL may have the possibility of further reducing the residual AS risk. Reverse cholesterol transport (RCT) is believed to be a primary atheroprotective activity of HDL, which has been shown to promote the efflux of excess cholesterol from macrophage-derived foam cells via ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), and scavenger receptor class B type I (SR-BI) and then transport it back to the liver for excretion into bile and eventually into the feces. In the current study, we investigated the effects of astaxanthin on RCT and AS progression in mice. The results showed that short- and long-term supplementation of astaxanthin promote RCT in C57BL/6J and ApoE-/- mice, respectively. Moreover, astaxanthin can relieve the plaque area of the aortic sinus and aortic cholesterol in mice. These findings suggest that astaxanthin is beneficial for boosting RCT and preventing the development of AS.

[Induction of robust senescence-associated secretory phenotype in mouse NIH-3T3 cells by mitomycin C].

Senescence-associated secretory phenotype (SASP) is often a concomitant result of cell senescence, embodied by the enhanced function of secretion. The SASP factors secreted by senescent cells include cytokines, proteases and chemokines, etc, which can exert great influence on local as well as systemic environment and participate in the process of cell senescence, immunoregulation, angiogenesis, cell proliferation and tumor invasion, etc. Relative to the abundance of SASP models in human cells, the in vitro SASP model derived from mouse cells is scarce at present. Therefore, the study aimed to establish a mouse SASP model to facilitate the research in the field. With this objective, we treated the INK4a-deficient mouse NIH-3T3 cells and the wildtype mouse embryonic fibroblasts (MEF) respectively with mitomycin C (MMC), an anticarcinoma drug which could induce DNA damage. The occurring of cell senescence was evaluated by cell morphology, ß-gal staining, integration ratio of EdU and Western blot. Quantitative RT-PCR and ELISA were used to detect the expression and secretion of SASP factors, respectively. The results showed that, 8 days after the treatment of NIH-3T3 cells with MMC (1 µg/mL) for 12 h or 24 h, the cells became enlarged and the ratios of ß-gal-positive (blue-stained) cells significantly increased, up to 77.4% and 90.4%, respectively. Meanwhile, the expression of P21 protein increased and the integration ratios of EdU significantly decreased (P < 0.01). Quantitative RT-PCR detection showed that the mRNA levels of several SASP genes, including IL-6, TNF-α, IL-1α and IL-1ß increased evidently. ELISA detection further observed an enhanced secretion of IL-6 (P < 0.01). On the contrary, although wildtype MEF could also be induced into senescence by MMC treatment for 12 h or 24 h, embodied by the enlarged cell volume, increased ratios of ß-gal-positive cells (up to 71.7% and 80.2%, respectively) and enhanced expression of P21 protein, the secretion of IL-6 displayed no significant change. Our study indicated that, although MMC could induce senescence in both mouse NIH-3T3 cells and wildtype MEF, only senescent NIH-3T3 cells displayed the canonical SASP phenomena. Current study suggested that senescent NIH-3T3 cells might be an appropriate in vitro SASP model of mouse cells.

PMT1 deficiency enhances basal UPR activity and extends replicative lifespan of Saccharomyces cerevisiae.

Pmt1p is an important member of the protein O-mannosyltransferase (PMT) family of enzymes, which participates in the endoplasmic reticulum (ER) unfolded protein response (UPR), an important pathway for alleviating ER stress. ER stress and the UPR have been implicated in aging and age-related diseases in several organisms; however, a possible role for PMT1 in determining lifespan has not been previously described. In this study, we report that deletion of PMT1 increases replicative lifespan (RLS) in the budding yeast Saccharomyces cerevisiae, while overexpression of PMT1 (PMT1-OX) reduces RLS. Relative to wild-type and PMT1-OX strains, the pmt1Δ strain had enhanced HAC1 mRNA splicing and elevated expression levels of UPR target genes. Furthermore, the increased RLS of the pmt1Δ strain could be completely abolished by deletion of either IRE1 or HAC1, two upstream modulators of the UPR. The double deletion strains pmt1Δhac1Δ and pmt1Δire1Δ also displayed generally reduced transcription of UPR target genes. Collectively, our results suggest that PMT1 deficiency enhances basal activity of the ER UPR and extends the RLS of yeast mother cells through a mechanism that requires both IRE1 and HAC1.

[New progresses of glaucoma research in China and abroad].

Great progresses have recently been made in glaucoma fields, including basic research and clinical management. This review covers major areas in the study of glaucoma, including epidemiology, pathogenesis, integrated imaging technology, medicine, laser and surgical therapy of glaucoma, as well as the new trends of development. This paper provides the future direction in the research of glaucoma.

[Regulatory volume decrease and its mechanism in nasopharyngeal epithelial cells].

To investigate regulatory volume decrease (RVD) and its mechanism in primary-culturing fetal human nasopharyngeal epithelial cells, living cell imaging technique was employed to detect the volume changes following exposure to hypotonic solution, and blockage of Cl- channels was used to clarify the role of Cl- channels in RVD. The results showed that extracellular hypotonic treatment swelled the cells and induced RVD. 47% hypotonic solution (160 mOsmol/L) swelled the cell by 144.7% and induced 38.7% recovery of cell volume within 20 min. RVD was correlated negatively to the extracellular osmolarity (r=-0.99, P<0.05) and positively to the swelling volume(r=0.99, P<0.05) in "S" shape, respectively. Chloride channel blockers, tamoxfen (20 micromol/ L), ATP (10 mmol/L) and NPPB (100 micromol/L), inhibited RVD by 100%, 76.3% and 62.7% (P< 0.01), respectively. The results indicated that primary-culturing fetal human nasopharyngeal epithelial cells are capable of RVD. Cl- efflux through Cl- channels is the key mechanism of RVD.

[Background chloride currents in fetal human nasopharyngeal epithelial cells].

To characterize the background current in fetal human nasopharyngeal epithelial cells and clarify its relationship with volume activated Cl(-) currents (I(Cl,vol)), whole-cell patch clamp and cell imaging techniques were employed. Under isotonic conditions, a background current [(5.9+/-2.1) pA/pF at +80 mV, n=21] was detected. The current presented a weak outward rectification and a negligible time-dependent inactivation. The current-voltage relationship showed that the reversal potential of the background current [(-0.73+/-1.7) mV, n=21] was close to the calculated equilibrium potential for Cl(-)(-0.9 mV). Application of extracellular hypertonic stimulation (440 mOsmol/L) suppressed the current by (59.6+/-7.1)% and the inhibition was reversible after returned to isotonic conditions. Bathing the cells in hypotonic solution (160 mOsmol/L) induced a volume-sensitive Cl(-) current. The Cl(-) channel blockers, tamoxifen (20 micromol/L) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) (100 micromol/L), inhibited the background current by (74.0+/-5.2)% (P<0.01, n=5) and (60.9+/-8.9)% (P<0.01, n=6) at +80 mV and increased basal cell volume by (107.7+/-2.9)% (P<0.01, n=25) and (104.4+/-2.4)% (P<0.01, n=19), respectively. The data indicate that Cl(-) current is an important component of the background current in fetal human nasopharyngeal epithelial cells. The background Cl(-) current is involved in volume activated Cl(-) current and basal cell volume regulation.

Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells.

The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5'-triphosphate (ATP), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of non-migrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relationship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells.

Activation of chloride current and decrease of cell volume by ATP in nasopharyngeal carcinoma cells.

Whole-cell patch clamp and cell volume measurement techniques were used to investigate the ATP-activated chloride current and the ATP effect on cell volume in nasopharyngeal carcinoma cells. Extracellular application of ATP in micromolar concentrations activated a current with the properties of modest outward rectification and negligible time-dependent inactivation in a dose-dependent manner. The current reversed at a potential [(-0.05+/-0.03) mV] close to the Cl- equilibrium potential (-0.9 mV). Substitution of Cl- with gluconate in the extracellular solution decreased the ATP-activated current and shifted the reversal potential positively. NPPB, one of the chloride channel blockers, inhibited the current by (81.03+/-9.36)%. The current was also depressed by the P2Y purinoceptor antagonist, reactive blue 2, by (67.39+/-5.06)%. ATP (50 micromol/L) decreased the cell volume under the isotonic condition. Depletion of extracellular and intracellular Cl- abolished the ATP effect on cell volume. The results suggest that extracellular ATP of micromolar scales can induce a chloride current associated with cell volume regulation by activation of chloride channel through binding to purinoceptor P2Y.

Volume-activated Cl- current in migrated nasopharyngeal carcinoma cells.

The transwell chamber migration assay and the patch-clamp technique were used to investigate the volume-activated Cl(-) current (I(Cl.vol)) in migrated nasopharyngeal carcinoma cells (CNE-2Z). 47% hypotonic solution activated a ICl.vol in the migrated CNE-2Z cells. Compared with the control cells (non-migrated), the properties of this current and the sensitivity to Cl(-) channel blockers were changed. The current density in migrated CNE-2Z cells was higher than that in non-migrated cells. The current was almost completely inhibited by extracellular application of adenosine-5'-triphosphate (ATP, 10 mmol/L), 5-nitro-2-3-phenylpropylamino benzoic acid (NPPB, 100 mmol/L) and tamoxifen (30 mmol/L) in all voltage steps applied. The inhibition of NPPB and tamoxifen on the current was stronger in migrated cells than that in non-migrated cells. The permeability sequence of the four anions was Br(-)>Cl(-)> I (-)>Gluconate. The sequence was different from that of the non-migrated cells (I(-)> Br(-)> Cl(-)> Gluconate). The results suggest that volume-activated chloride channels may be involved in the CNE-2Z cell migration.