Evaluation of the Cardiotoxicity of Mitragynine and Its Analogues Using Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Introduction

Mitragynine is a major bioactive compound of Kratom, which is derived from the leave extracts of Mitragyna speciosa Korth or Mitragyna speciosa (M. speciosa), a medicinal plant from South East Asia used legally in many countries as stimulant with opioid-like effects for the treatment of chronic pain and opioid-withdrawal symptoms. Fatal incidents with Mitragynine have been associated with cardiac arrest. In this study, we determined the cardiotoxicity of Mitragynine and other chemical constituents isolated using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

Methods and Results

The rapid delayed rectifier potassium current (I _Kr), L-type Ca²⁺ current (I _Ca,L) and action potential duration (APD) were measured by whole cell patch-clamp. The expression of KCNH2 and cytotoxicity was determined by real-time PCR and Caspase activity measurements. After significant I _Kr suppression by Mitragynine (10 µM) was confirmed in hERG-HEK cells, we systematically examined the effects of Mitragynine and other chemical constituents in hiPSC-CMs. Mitragynine, Paynantheine, Speciogynine and Speciociliatine, dosage-dependently (0.1∼100 µM) suppressed I _Kr in hiPSC-CMs by 67% ∼84% with IC₅₀ ranged from 0.91 to 2.47 µM. Moreover, Mitragynine (10 µM) significantly prolonged APD at 50 and 90% repolarization (APD50 and APD90) (439.0±11.6 vs. 585.2±45.5 ms and 536.0±22.6 vs. 705.9±46.1 ms, respectively) and induced arrhythmia, without altering the L-type Ca²⁺ current. Neither the expression,and intracellular distribution of KCNH2/Kv11.1, nor the Caspase 3 activity were significantly affected by Mitragynine.

Conclusions

Our study indicates that Mitragynine and its analogues may potentiate Torsade de Pointes through inhibition of I _Kr in human cardiomyocytes.     

Molecular Analysis of RNF213 Gene for Moyamoya Disease in the Chinese Han Population

Background

Moyamoya disease (MMD) is an uncommon cerebrovascular disorder characterized by progressive occlusion of the internal carotid artery causing cerebral ischemia and hemorrhage. Genetic factors in the etiology and pathogenesis of MMD are being increasingly recognized. Previous studies have shown that the RNF213 gene was related to MMD susceptibility in the Japanese population. However, there is no large scale study of the association between this gene and MMD in the Chinese Han population. Thus we designed this case-control study to validate the R4810K mutation and to define the further spectrum of RNF213 mutations in Han Chinese.

Methodology/Principal Findings

Genotyping of the R4810K mutation in the RNF213 gene was performed in 170 MMD cases and 507 controls from a Chinese Han population. The R4810K mutation was identified in 22 of 170 MMD cases (13%), including 21 heterozygotes and a single familial homozygote. Two of the 507 controls (0.4%) were heterozygous R4810K carriers. The R4810K mutation greatly increased the risk for MMD (OR = 36.7, 95% CI: 8.6∼156.6, P = 6.1 E-15). The allele frequency of R4810K was significantly different between patients with ischemia and hemorrhage (OR = 5.4, 95% CI: 1.8∼16.1, P = 0.001). Genomic sequencing covering RNF213 exon 40 to exon 68 also identified eight other non-R4810K variants; P4007R, Q4367L, A4399T, T4586P, L4631V, E4950D, A5021V and M5136I. Among them A4399T polymorphism was found in 28/170 cases (16.5%) and 45/507 controls (8.9%) and was associated with MMD (OR = 2.0, 95% CI: 1.2∼3.3, P = 0.004), especially with hemorrhage (OR = 2.8, 95% CI: 1.2∼6.5, P = 0.014).

Conclusions

RNF213 mutations are associated with MMD susceptibility in Han Chinese. The ischemic type MMD is particularly related to the R4810K mutation. However, A4399T is also a susceptible variant for MMD, primarily associated with hemorrhage. Identification of novel variants in the RNF213 gene further highlights the genetic heterogeneity of MMD.     

Action Potential Clamp and Pharmacology of the Variant 1 Short QT Syndrome T618I hERG K+ Channel

Background

The familial Short QT Syndrome (SQTS) is associated with an increased risk of cardiac arrhythmia and sudden death. Gain-of-function mutations in the hERG K⁺ channel protein have been linked to variant 1 of the SQTS. A hERG channel pore (T618I) mutation has recently been identified in families with heritable SQTS. This study aimed to determine effects of the T618I-hERG mutation on (i) hERG current (I_hERG) elicited by ventricular action potentials; (ii) the sensitivity of I_hERG to inhibition by four clinically used antiarrhythmic drugs.

Methods

Electrophysiological recordings of I_hERG were made at 37°C from HEK 293 cells expressing wild-type (WT) or T618I hERG. Whole-cell patch clamp recording was performed using both conventional voltage clamp and ventricular action potential (AP) clamp methods.

Results

Under conventional voltage-clamp, WT I_hERG peaked at 0-+10 mV, whilst for T618I I_hERG maximal current was right-ward shifted to ∼ +40 mV. Voltage-dependent activation and inactivation of T618I I_hERG were positively shifted (respectively by +15 and ∼ +25 mV) compared to WT I_hERG. The I_hERG ‘window’ was increased for T618I compared to WT hERG. Under ventricular AP clamp, maximal repolarising WT I_hERG occurred at ∼ -30 mV, whilst for T618I hERG peak I_hERG occurred earlier during AP repolarisation, at ∼ +5 mV. Under conventional voltage clamp, half-maximal inhibitory concentrations (IC₅₀) for inhibition of I_hERG tails by quinidine, disopyramide, D-sotalol and flecainide for T618I hERG ranged between 1.4 and 3.2 fold that for WT hERG. Under action potential voltage clamp, T618I IC₅₀s ranged from 1.2 to 2.0 fold the corresponding IC₅₀ values for WT hERG.

Conclusions

The T618I mutation produces a more modest effect on repolarising I_hERG than reported previously for the N588K-hERG variant 1 SQTS mutation. All drugs studied here appear substantially to retain their ability to inhibit I_hERG in the setting of the SQTS-linked T618I mutation.     

Long QT Interval in Turner Syndrome – A High Prevalence of LQTS Gene Mutations

Objectives

QT-interval prolongation of unknown aetiology is common in Turner syndrome. This study set out to explore the presence of known long QT mutations in Turner syndrome and to examine the corrected QT-interval (QTc) over time and relate the findings to the Turner syndrome phenotype.

Methods

Adult women with Turner syndrome (n = 88) were examined thrice and 68 age-matched healthy controls were examined once. QTc was measured by one blinded reader (intra-reader variability: 0.7%), and adjusted for influence of heart rate by Bazett’s (bQTc) and Hodges’s formula (hQTc). The prevalence of mutations in genes related to Long QT syndrome was determined in women with Turner syndrome and a QTc >432.0 milliseconds (ms). Echocardiographic assessment of aortic valve morphology, 24-hour blood pressures and blood samples were done.

Results

The mean hQTc in women with Turner syndrome (414.0±25.5 ms) compared to controls (390.4±17.8 ms) was prolonged (p<0.001) and did not change over time (416.9±22.6 vs. 415.6±25.5 ms; p = 0.4). 45,X karyotype was associated with increased hQTc prolongation compared to other Turner syndrome karyotypes (418.2±24.8 vs. 407.6±25.5 ms; p = 0.055). In women with Turner syndrome and a bQTc >432 ms, 7 had mutations in major Long QT syndrome genes (SCN5A and KCNH2) and one in a minor Long QT syndrome gene (KCNE2).

Conclusion

There is a high prevalence of mutations in the major LQTS genes in women with TS and prolonged QTc. It remains to be settled, whether these findings are related to the unexplained excess mortality in Turner women.

Clinical Trial Registration

{"type":"clinical-trial","attrs":{"text":"NCT00624949","term_id":"NCT00624949"}}NCT00624949. https://register.clinicaltrials.gov/prs/app/action/SelectProtocol/sid/S0001FLI/selectaction/View/ts/3/uid/U000099E.     

Overlapping LQT1 and LQT2 phenotype in a patient with long QT syndrome associated with loss-of-function variations in KCNQ1 and KCNH2

Long QT syndrome (LQTS) is an inherited disorder characterized by prolonged QT intervals and potentially life-threatening arrhythmias. Mutations in 12 different genes have been associated with LQTS. Here we describe a patient with LQTS who has a mutation in KCNQ1 as well as a polymorphism in KCNH2. The proband (MMRL0362), a 32-year-old female, exhibited multiple ventricular extrasystoles and one syncope. Her ECG (QT interval corrected for heart rate (QTc) = 518ms) showed an LQT2 morphology in leads V4-V6 and LQT1 morphology in leads V1-V2. Genomic DNA was isolated from lymphocytes. All exons and intron borders of 7 LQTS susceptibility genes were amplified and sequenced. Variations were detected predicting a novel missense mutation (V110I) in KCNQ1, as well as a common polymorphism in KCNH2 (K897T). We expressed wild-type (WT) or V110I Kv7.1 channels in CHO-K1 cells cotransfected with KCNE1 and performed patch-clamp analysis. In addition, WT or K897T Kv11.1 were also studied by patch clamp. Current-voltage (I-V) relations for V110I showed a significant reduction in both developing and tail current densities compared with WT at potentials >+20 mV (p < 0.05; n = 8 cells, each group), suggesting a reduction in IKs currents. K897T- Kv11.1 channels displayed a significantly reduced tail current density compared with WT-Kv11.1 at potentials >+10 mV. Interestingly, channel availability assessed using a triple-pulse protocol was slightly greater for K897T compared with WT (V0.5 = -53.1 ± 1.13 mV and -60.7 ± 1.15 mV for K897T and WT, respectively; p < 0.05). Comparison of the fully activated I-V revealed no difference in the rectification properties between WT and K897T channels. We report a patient with a loss-of-function mutation in KCNQ1 and a loss-of-function polymorphism in KCNH2. Our results suggest that a reduction of both IKr and IKs underlies the combined LQT1 and LQT2 phenotype observed in this patient.     

The Duration of a Co-Occurring Sound Modulates Visual Detection Performance in Humans

Background

The duration of sounds can affect the perceived duration of co-occurring visual stimuli. However, it is unclear whether this is limited to amodal processes of duration perception or affects other non-temporal qualities of visual perception.

Methodology/Principal Findings

Here, we tested the hypothesis that visual sensitivity - rather than only the perceived duration of visual stimuli - can be affected by the duration of co-occurring sounds. We found that visual detection sensitivity (d’) for unimodal stimuli was higher for stimuli of longer duration. Crucially, in a cross-modal condition, we replicated previous unimodal findings, observing that visual sensitivity was shaped by the duration of co-occurring sounds. When short visual stimuli (∼24 ms) were accompanied by sounds of matching duration, visual sensitivity was decreased relative to the unimodal visual condition. However, when the same visual stimuli were accompanied by longer auditory stimuli (∼60–96 ms), visual sensitivity was increased relative to the performance for ∼24 ms auditory stimuli. Across participants, this sensitivity enhancement was observed within a critical time window of ∼60–96 ms. Moreover, the amplitude of this effect correlated with visual sensitivity enhancement found for longer lasting visual stimuli across participants.

Conclusions/Significance

Our findings show that the duration of co-occurring sounds affects visual perception; it changes visual sensitivity in a similar way as altering the (actual) duration of the visual stimuli does.     

Comparisons of GnRH Antagonist versus GnRH Agonist Protocol in Supposed Normal Ovarian Responders Undergoing IVF: A Systematic Review and Meta-Analysis

Objective

To evaluate the effectiveness and safety of GnRH antagonist and GnRH agonist in supposed normal ovarian responders undergoing IVF.

Methods

Data from 6 databases were retrieved for this study. The RCTs of GnRH agonist and GnRH antagonist use during IVF-EF therapy for patients with supposed normal ovarian response were included. A meta-analysis was performed with Revman 5.1software.

Results

Twenty-three RCTs met the inclusion criteria. The number of stimulation days (mean difference (MD): −0.66, 95% confidence interval (CI): −1.04∼−0.27), Gn amount (MD: −2.92, 95% CI: −5.0∼−0.85), E2 values on the day of HCG (MD: −330.39, 95% CI: −510.51∼−150.26), Number of oocytes retrieved (MD: −1.33, 95% CI: −2.02∼−0.64), clinical pregnancy rate (odds ratio (OR): 0.87, 95% CI: 0.75−1.0), and ovarian hyperstimulation syndrome (OHSS) incidence (OR: 0.59, 95% CI: 0.42∼0.82) were significantly lower in GnRH antagonist protocol than GnRH agonist protocol. However, the endometrial thickness on the day of HCG (MD: −0.04, 95% CI: −0.23∼0.14), the ongoing pregnancy rate (OR: 0.87, 95% CI: 0.74∼1.03), live birth rate (OR: 0.89, 95% CI: 0.64∼1.24), miscarriage rate (OR: 1.17, 95% CI: 0.85∼1.61), and cycle cancellation rate (OR: 1.11, 95% CI: 0.90∼1.37) did not significantly differ between the 2 groups.

Conclusions

During IVF treatment for patients with supposed normal responses, the incidence of OHSS were significantly lower, whereas the ongoing pregnancy and live birth rates were similar in the GnRH antagonist compared with the standard long GnRH agonist protocols.     

Total Beta-Adrenoceptor Knockout Slows Conduction and Reduces Inducible Arrhythmias in the Mouse Heart

Introduction

Beta-adrenoceptors (β-AR) play an important role in the neurohumoral regulation of cardiac function. Three β-AR subtypes (β₁, β₂, β₃) have been described so far. Total deficiency of these adrenoceptors (TKO) results in cardiac hypotrophy and negative inotropy. TKO represents a unique mouse model mimicking total unselective medical β-blocker therapy in men. Electrophysiological characteristics of TKO have not yet been investigated in an animal model.

Methods

In vivo electrophysiological studies using right heart catheterisation were performed in 10 TKO mice and 10 129SV wild type control mice (WT) at the age of 15 weeks. Standard surface ECG, intracardiac and electrophysiological parameters, and arrhythmia inducibility were analyzed.

Results

The surface ECG of TKO mice revealed a reduced heart rate (359.2±20.9 bpm vs. 461.1±33.3 bpm; p<0.001), prolonged P wave (17.5±3.0 ms vs. 15.1±1.2 ms; p = 0.019) and PQ time (40.8±2.4 ms vs. 37.3±3.0 ms; p = 0.013) compared to WT. Intracardiac ECG showed a significantly prolonged infra-Hisian conductance (HV-interval: 12.9±1.4 ms vs. 6.8±1.0 ms; p<0.001). Functional testing showed prolonged atrial and ventricular refractory periods in TKO (40.5±15.5 ms vs. 21.3±5.8 ms; p = 0.004; and 41.0±9.7 ms vs. 28.3±6.6 ms; p = 0.004, respectively). In TKO both the probability of induction of atrial fibrillation (12% vs. 24%; p<0.001) and of ventricular tachycardias (0% vs. 26%; p<0.001) were significantly reduced.

Conclusion

TKO results in significant prolongations of cardiac conduction times and refractory periods. This was accompanied by a highly significant reduction of atrial and ventricular arrhythmias. Our finding confirms the importance of β-AR in arrhythmogenesis and the potential role of unspecific beta-receptor-blockade as therapeutic target.     

Activation of the Left Inferior Frontal Gyrus in the First 200 ms of Reading: Evidence from Magnetoencephalography (MEG)

Background

It is well established that the left inferior frontal gyrus plays a key role in the cerebral cortical network that supports reading and visual word recognition. Less clear is when in time this contribution begins. We used magnetoencephalography (MEG), which has both good spatial and excellent temporal resolution, to address this question.

Methodology/Principal Findings

MEG data were recorded during a passive viewing paradigm, chosen to emphasize the stimulus-driven component of the cortical response, in which right-handed participants were presented words, consonant strings, and unfamiliar faces to central vision. Time-frequency analyses showed a left-lateralized inferior frontal gyrus (pars opercularis) response to words between 100–250 ms in the beta frequency band that was significantly stronger than the response to consonant strings or faces. The left inferior frontal gyrus response to words peaked at ∼130 ms. This response was significantly later in time than the left middle occipital gyrus, which peaked at ∼115 ms, but not significantly different from the peak response in the left mid fusiform gyrus, which peaked at ∼140 ms, at a location coincident with the fMRI–defined visual word form area (VWFA). Significant responses were also detected to words in other parts of the reading network, including the anterior middle temporal gyrus, the left posterior middle temporal gyrus, the angular and supramarginal gyri, and the left superior temporal gyrus.

Conclusions/Significance

These findings suggest very early interactions between the vision and language domains during visual word recognition, with speech motor areas being activated at the same time as the orthographic word-form is being resolved within the fusiform gyrus. This challenges the conventional view of a temporally serial processing sequence for visual word recognition in which letter forms are initially decoded, interact with their phonological and semantic representations, and only then gain access to a speech code.     

Dysfunctional Behavioral Modulation of Corticostriatal Communication in the R6/2 Mouse Model of Huntington’s Disease

Background

In Huntington’s disease (HD), motor symptoms develop prior to the widespread loss of neurons in striatum and cerebral cortex. The aim of this study was to examine dysfunctional patterns of corticostriatal communication during spontaneously occurring behaviors in a transgenic mouse model of HD.

Methodology/Principal Findings

Local field potentials (LFPs) were recorded from two closely interconnected areas, motor cortex and dorsal striatum, in wild-type controls (WT, n = 14) and a widely used transgenic HD model (R6/2 mice, n = 12). All mice were between the ages of 7–9 weeks, a critical period of motor symptom development in R6/2s. Recordings were obtained while the mice were behaving freely in an open field. Specific LFP activity was extracted using timestamps for three increasingly demanding motor behaviors: 1) resting; 2) grooming; and 3) active exploration. Power spectral densities (PSD) were obtained for the cortical and striatal LFPs as well as coherence levels and relative phase across the frequency spectrum. In both brain regions, only R6/2s showed high frequency LFP oscillations during rest and grooming. As behavior increased from resting to exploring, corticostriatal synchrony at high frequencies declined in R6/2s, completely opposite to the WT pattern. R6/2s also exhibited nearly in-phase corticostriatal activity (cortex phase leads of ∼5°), while the WTs consistently showed cortical phase lags of ∼20° across all assessed behaviors, indicating a lead role for striatum.

Conclusions/Significance

Our results add to growing evidence for altered communication between cortex and striatum in HD and suggest more generally that increasingly demanding motor behaviors differentially modulate corticostriatal communication. Our data also suggest conduction delays in R6/2 corticostriatal transmission, leading to compensatory speeding of LFP activity, as evidenced by the presence of high frequency LFP oscillations.     

Meta-Analysis of Randomized Controlled Trials Comparing Latanoprost with Timolol in the Treatment of Asian Populations with Chronic Angle-Closure Glaucoma

Background

To evaluate the efficacy and safety of latanoprost compared with timolol in the treatment of Asian patients with chronic angle-closure glaucoma (CACG).

Methods

Relevant trials were identified through systematic searches of Medline, EMBASE, PubMed, Cochrane Library, Google Scholar and several Chinese databases. The main outcome measures included absolute and relative reduction of intraocular pressure (IOP) at mean, peak and trough from baseline, ocular adverse effects and systemic adverse events.

Results

Seven randomized controlled trials with 685 patients were included. In comparison with timolol, latanoprost reduced absolute IOP in CACG patients by more than 2.3 mmHg (95%CI, 1.8∼2.9, P<0.01), 2.4 mmHg (95%CI, 1.9∼2.9, P<0.01) and 2.5 mmHg (95%CI, 1.6∼3.3, P<0.01) at mean, peak and trough, respectively. As for relative IOP, there is 9.0% (95%CI, 6.6∼11.4, P<0.01), 9.7% (95%CI, 7.6∼11.8, P<0.01), and 10.8% (95%CI, 7.4∼14.3, P<0.01) greater reduction among latanoprost users than among timolol users. The differences were statistically significant at all time points (1, 2, 4, 8, 12, and 24 weeks). More ocular adverse effects (OR = 1.49, 95% CI, 1.05∼2.10, P = 0.02) and less systemic adverse events (OR = 0.46, 95% CI, 0.25∼0.84, P = 0.01) were observed in latanoprost group in comparison with timolol group.

Conclusion

Compared with timolol, latanoprost was significantly more effective in lowering IOP of Asian patients with CACG, with higher risk of ocular adverse effects but lower risk of systemic adverse events, and might be a good substitute for CACG patients.     

Comparison of Sum Absolute QRST Integral,and Temporal Variability in Depolarization and Repolarization,Measured by Dynamic Vectorcardiography Approach,in Healthy Men and Women

Background

Recently we showed the predictive value of sum absolute QRST integral (SAI QRST) and repolarization lability for risk stratification of sudden cardiac death (SCD) in heart failure patients. The goal of this study was to compare SAI QRST and metrics of depolarization and repolarization variability in healthy men and women.

Methods

Orthogonal ECGs were recorded at rest for 10 minutes in 160 healthy men and women (mean age 39.6±14.6, 80 men). Mean spatial TT′ angle, and normalized variances of T loop area, of spatial T vector amplitude, of QT interval and Tpeak-Tend area were measured for assessment of repolarization lability. Normalized variances of spatial QRS vector and QRS loop area characterized variability of depolarization. In addition, variability indices (VI) were calculated to adjust for normalized heart rate variance. SAI QRST was measured as the averaged arithmetic sum of areas under the QRST curve.

Results

Men were characterized by shorter QTc (430.3±21.7 vs. 444.7±22.2 ms; P<0.0001) and larger SAI QRST (282.1±66.7 vs.204.9±58.5 mV*ms; P<0.0001). Repolarization lability negatively correlated with spatial T vector amplitude. Adjusted by normalized heart rate variance, QT variability index was significantly higher in women than in men (−1.54±0.38 vs. −1.70±0.33; P = 0.017). However, in multivariate logistic regression after adjustment for body surface area, QTc, and spatial T vector amplitude, healthy men had 1.5–3 fold higher probability of having larger repolarization lability, as compared to healthy women (T vector amplitude variability index odds ratio 3.88(95%CI 1.4–11.1; P = 0.012).

Conclusions

Healthy men more likely than women have larger repolarization lability.     

The KCNH2 Genetic Polymorphism (1956, C>T) Is a Novel Biomarker That Is Associated with CCB and α,β-ADR Blocker Response in EH Patients in China

Background

KCNH2 (hERG) potassium channels have an integral role in regulating the excitability of smooth muscle cells. Some pathways driven by angiotensin II, nitric oxide and adrenergic receptors blocker are involved in modulating the properties of KCNH2 potassium channels. And these pathways are closely related to blood pressure regulation. Therefore, we hypothesized that KCNH2 genetic polymorphisms may affect blood pressure response to the antihypertensive drug therapies.

Materials and Methods

To evaluate the interactions between KCNH2 genetic polymorphisms and individual blood pressure response to antihypertensive drugs, 370 subjects with essential hypertension (EH) were studied. In evaluating the interactions between KCNH2 genetic polymorphisms and drug response to blood pressure, multivariable ANOVA analysis followed by Bonferroni correction were carried out.

Results

There were statistically significant interactions between KCNH2 (1956, C>T) polymorphism and DBP change (P = 0.010), MAP change (P = 0.014) on azelnidipine or nitrendipine therapy patients at the end of 6 weeks. We found that the KCNH2 (1956,C>T) polymorphism was associated with the hypotensive effects of α,β-ADR blockers of DBP change at the end of 4 and 6 weeks'' treatment in an age- and gender-dependent manner (P = 0.007 and 0.019, respectively). Similar results were also observed for changes in MAP at the end of 4 and 6 weeks (P-values were 0.035 and 0.078, respectively). While patients who received imidapril, candesartan and irbesartan therapy, no significant difference in drug response among KCNH2(1956,C>T) genotype was observed.

Conclusion

We have reported for the first time that KCNH2 (1956, C>T) polymorphism is associated with efficacy of antihypertensive drugs CCBs and ADR blockers, and may serve as a novel biomarker for individualized therapy for certain antihypertensive drugs.     

Pronounced Effects of HERG-Blockers E-4031 and Erythromycin on APD,Spatial APD Dispersion and Triangulation in Transgenic Long-QT Type 1 Rabbits

Background

Prolongation of action potential duration (APD), increased spatial APD dispersion, and triangulation are major factors promoting drug-induced ventricular arrhythmia. Preclinical identification of HERG/I_Kr-blocking drugs and their pro-arrhythmic potential, however, remains a challenge. We hypothesize that transgenic long-QT type 1 (LQT1) rabbits lacking repolarizing I_Ks current may help to sensitively detect HERG/I_Kr-blocking properties of drugs.

Methods

Hearts of adult female transgenic LQT1 and wild type littermate control (LMC) rabbits were Langendorff-perfused with increasing concentrations of HERG/I_Kr-blockers E-4031 (0.001–0.1 µM, n = 9/7) or erythromycin (1–300 µM, n = 9/7) and APD, APD dispersion, and triangulation were analyzed.

Results

At baseline, APD was longer in LQT1 than in LMC rabbits in LV apex and RV mid. Erythromycin and E-4031 prolonged APD in LQT1 and LMC rabbits in all positions. However, erythromycin-induced percentaged APD prolongation related to baseline (%APD) was more pronounced in LQT1 at LV base-lateral and RV mid positions (100 µM, LQT1, +40.6±9.7% vs. LMC, +24.1±10.0%, p<0.05) and E-4031-induced %APD prolongation was more pronounced in LQT1 at LV base-lateral (0.01 µM, LQT1, +29.6±10.6% vs. LMC, +19.1±3.8%, p<0.05) and LV base-septal positions. Moreover, erythromycin significantly increased spatial APD dispersion only in LQT1 and increased triangulation only in LQT1 in LV base-septal and RV mid positions. Similarly, E-4031 increased triangulation only in LQT1 in LV apex and base-septal positions.

Conclusions

E-4031 and erythromycin prolonged APD and increased triangulation more pronouncedly in LQT1 than in LMC rabbits. Moreover, erythromycin increased APD dispersion only in LQT1, indicating that transgenic LQT1 rabbits could serve as sensitive model to detect HERG/I_Kr-blocking properties of drugs.     

Teicoplanin as an Effective Alternative to Vancomycin for Treatment of MRSA Infection in Chinese Population: A Meta-analysis of Randomized Controlled Trials

Objective

To evaluate whether teicoplanin could be an alternative to vancomycin for treatment of MRSA infection in Chinese population using a meta-analysis in randomized controlled trials.

Methods

The following databases were searched: Chinese Biomedical Literature database (CBM), Chinese Journal Full-text database (CNKI), Wanfang database, Medline database, Ovid database and Cochrane Library. Articles published from 2002 to 2013 that studied teicoplanin in comparison to vancomycin in the treatment of MRSA infected patients were collected. Overall effects, publishing bias analysis and sensitivity analysis on clinical cure rate, microbiologic eradication rate and adverse events rate were performed by using Review Manager 5.2 and Stata 11.0 softwares.

Results

Twelve articles met entry criteria. There was no statistically significant difference between the two groups regarding the clinical cure rate (risk ratio [RR], teicoplanin vs vancomycin, 0.94; 95% CI, 0.74∼1.19; P = 0.60), microbiological cure rate (risk ratio [RR], teicoplanin vs vancomycin, 0.99; 95% CI, 0.91∼1.07; P = 0.74) and adverse event rate (risk ratio [RR], teicoplanin vs vancomycin, 0.86; 95% CI, 0.40∼1.84; P = 0.70).

Conclusions

The meta-analysis results indicate that the two therapies are similar in both efficacy and safety, thus teicoplanin can act as an effective alternative to vancomycin for treating patients infected by MRSA.     

Involvement of the Same TNFR1 Residue in Mendelian and Multifactorial Inflammatory Disorders

Objectives

TNFRSF1A is involved in an autosomal dominant autoinflammatory disorder called TNFR-associated periodic syndrome (TRAPS). Most TNFRSF1A mutations are missense changes and, apart from those affecting conserved cysteines, their deleterious effect remains often questionable. This is especially true for the frequent R92Q mutation, which might not be responsible for TRAPS per se but represents a susceptibility factor to multifactorial inflammatory disorders. This study investigates TRAPS pathophysiology in a family exceptional by its size (13 members) and compares the consequences of several mutations affecting arginine 92.

Methods

TNFRSF1A screening was performed by PCR-sequencing. Comparison of the 3-dimensional structure and electrostatic properties of wild-type and mutated TNFR1 proteins was performed by in silico homology modeling. TNFR1 expression was assessed by FACS analysis, western blotting and ELISA in lysates and supernatants of HEK293T cells transiently expressing wild-type and mutated TNFR1.

Results

A TNFRSF1A heterozygous missense mutation, R92W (c.361C>T), was shown to perfectly segregate with typical TRAPS manifestations within the family investigated (p<5.10⁻⁴). It was associated with very high disease penetrance (0.9). Prediction of its impact on the protein structure revealed local conformational changes and alterations of the receptor electrostatic properties. R92W also impairs the TNFR1 expression at the cell surface and the levels of soluble receptor. Similar results were obtained with R92P, another mutation previously identified in a very small familial form with incomplete penetrance and variable expressivity. In contrast, TNFR1-R92Q behaves like the wild-type receptor.

Conclusions

These data demonstrate the pathogenicity of a mutation affecting arginine 92, a residue whose involvement in inflammatory disorders is deeply debated. Combined with previous reports on arginine 92 mutations, this study discloses an unusual situation in which different amino acid substitutions at the same position in the protein are associated with a clinical spectrum bridging Mendelian to multifactorial conditions.     

Evaluation of Differences in Automated QT/QTc Measurements between Fukuda Denshi and Nihon Koden Systems

Background

Automatic measurement becomes a preference, and indeed a necessity, when analyzing 1000 s of ECGs in the setting of either drug-inducing QT prolongation screening or genome-wide association studies of QT interval. The problem is that individual manufacturers apply different computerized algorithms to measure QT interval. We conducted a comparative study to assess the outcomes with different automated measurements of QT interval between ECG machine manufacturers and validated the related heart rate correction methods.

Methods and Results

Herein, we directly compared these different commercial systems using 10,529 Fukuda Denshi ECGs and 72,754 Nihon Kohden ECGs taken in healthy Japanese volunteers. Log-transformed data revealed an equal optimal heart rate correction formula of QT interval for Fukuda Denshi and Nihon Kohden, in the form of QTc = QT/RR^−0.347. However, with the raw data, the optimal heart rate correction formula of QT interval was in the form of QTc = QT+0.156×(1-RR) for Fukuda Denshi and QTc = QT+0.152×(1-RR) for Nihon Kohden. After optimization of heart rate correction of QT interval by the linear regression model using either log-transformed data or raw data, QTc interval was ∼10 ms longer in Nihon Kohden ECGs than in those recorded on Fukuda Denshi machines. Indeed, regression analysis revealed that differences in the ECG machine used had up to a two-fold larger impact on QT variation than gender difference. Such an impact is likely to be of considerable importance when ECGs for a given individual are recorded on different machines in the setting of multi-institutional joint research.

Conclusions

We recommend that ECG machines of the same manufacturer should be used to measure QT and RR intervals in the setting of multi-institutional joint research. It is desirable to unify the computer algorithm for automatic QT and RR measurements from an ECG.     

Funding Infectious Disease Research: A Systematic Analysis of UK Research Investments by Funders 1997–2010

Background

Research investments are essential to address the burden of disease, however allocation of limited resources is poorly documented. We systematically reviewed the investments awarded by funding organisations to UK institutions and their global partners for infectious disease research.

Methodology/Principal Findings

Public and philanthropic investments for the period 1997 to 2010 were included. We categorised studies by infectious disease, cross-cutting theme, and by research and development value chain, reflecting the type of science. We identified 6165 funded studies, with a total research investment of UK £2.6 billion. Public organisations provided £1.4 billion (54.0%) of investments compared with £1.1 billion (42.4%) by philanthropic organisations. Global health studies represented an investment of £928 million (35.7%). The Wellcome Trust was the leading investor with £688 million (26.5%), closely followed by the UK Medical Research Council (MRC) with £673 million (25.9%). Funding over time was volatile, ranging from ∼£40 million to ∼£160 million per year for philanthropic organisations and ∼£30 million to ∼£230 million for public funders.

Conclusions/Significance

Infectious disease research funding requires global coordination and strategic long-term vision. Our analysis demonstrates the diversity and inconsistent patterns in investment, with volatility in annual funding amounts and limited investment for product development and clinical trials.     

Hawk Eyes I: Diurnal Raptors Differ in Visual Fields and Degree of Eye Movement

Background

Different strategies to search and detect prey may place specific demands on sensory modalities. We studied visual field configuration, degree of eye movement, and orbit orientation in three diurnal raptors belonging to the Accipitridae and Falconidae families.

Methodology/Principal Findings

We used an ophthalmoscopic reflex technique and an integrated 3D digitizer system. We found inter-specific variation in visual field configuration and degree of eye movement, but not in orbit orientation. Red-tailed Hawks have relatively small binocular areas (∼33°) and wide blind areas (∼82°), but intermediate degree of eye movement (∼5°), which underscores the importance of lateral vision rather than binocular vision to scan for distant prey in open areas. Cooper''s Hawks'' have relatively wide binocular fields (∼36°), small blind areas (∼60°), and high degree of eye movement (∼8°), which may increase visual coverage and enhance prey detection in closed habitats. Additionally, we found that Cooper''s Hawks can visually inspect the items held in the tip of the bill, which may facilitate food handling. American Kestrels have intermediate-sized binocular and lateral areas that may be used in prey detection at different distances through stereopsis and motion parallax; whereas the low degree eye movement (∼1°) may help stabilize the image when hovering above prey before an attack.

Conclusions

We conclude that: (a) there are between-species differences in visual field configuration in these diurnal raptors; (b) these differences are consistent with prey searching strategies and degree of visual obstruction in the environment (e.g., open and closed habitats); (c) variations in the degree of eye movement between species appear associated with foraging strategies; and (d) the size of the binocular and blind areas in hawks can vary substantially due to eye movements. Inter-specific variation in visual fields and eye movements can influence behavioral strategies to visually search for and track prey while perching.     

Impaired ion channel function related to a common KCNQ1 mutation — Implications for risk stratification in long QT syndrome 1

Long QT syndrome (LQTS) 1 is the most common type of inherited LQTS and is linked to mutations in the KCNQ1 gene. We identified a KCNQ1 missense mutation, KCNQ1 G325R, in an asymptomatic patient presenting with significant QT prolongation (QTc, 448–600 ms). Prior clinical reports revealed phenotypic variability ranging from the absence of symptoms to syncope among KCNQ1 G325R mutation carriers. The present study was designed to determine the G325R ion channel phenotype and its association with the clinical LQTS presentation. Electrophysiological testing was performed using the Xenopus oocyte expression system. KCNQ1 G325R channels were non-functional and suppressed wild type (WT) currents by 71.1%. In the presence of the native cardiac regulatory ß-subunit, KCNE1, currents conducted by G325R and WT KCNQ1 were reduced by 52.9%. Co-expression of G325R and WT KCNQ1 with KCNE1 shifted the voltage-dependence of I_Ks activation by 12.0 mV, indicating co-assembly of mutant and WT subunits. The dysfunctional biophysical phenotype validates the pathogenicity of the KCNQ1 G325R mutation and corresponds well with the severe clinical presentation revealed in some reports. However, the index patient and other mutation carriers were asymptomatic, highlighting potential limitations of risk assessment schemes based on ion channel data.