Electrophysiologic effects of the IK1 inhibitor PA-6 are modulated by extracellular potassium in isolated guinea pig hearts

The pentamidine analog PA‐6 was developed as a specific inward rectifier potassium current (I(K) (1)) antagonist, because established inhibitors either lack specificity or have side effects that prohibit their use in vivo. We previously demonstrated that BaCl(2), an established I(K) (1) inhibitor, could prolong action potential duration (APD) and increase cardiac conduction velocity (CV). However, few studies have addressed whether targeted I(K) (1) inhibition similarly affects ventricular electrophysiology. The aim of this study was to determine the effects of PA‐6 on cardiac repolarization and conduction in Langendorff‐perfused guinea pig hearts. PA‐6 (200 nm) or vehicle was perfused into ex‐vivo guinea pig hearts for 60 min. Hearts were optically mapped with di‐4‐ANEPPS to quantify CV and APD at 90% repolarization (APD (90)). Ventricular APD (90) was significantly prolonged in hearts treated with PA‐6 (115 ± 2% of baseline; P < 0.05), but not vehicle (105 ± 2% of baseline). PA‐6 slightly, but significantly, increased transverse CV by 7%. PA‐6 significantly prolonged APD (90) during hypokalemia (2 mmol/L [K+](o)), although to a lesser degree than observed at 4.56 mmol/L [K+](o). In contrast, the effect of PA‐6 on CV was more pronounced during hypokalemia, where transverse CV with PA‐6 (24 ± 2 cm/sec) was significantly faster than with vehicle (13 ± 3 cm/sec, P < 0.05). These results show that under normokalemic conditions, PA‐6 significantly prolonged APD (90), whereas its effect on CV was modest. During hypokalemia, PA‐6 prolonged APD (90) to a lesser degree, but profoundly increased CV. Thus, in intact guinea pig hearts, the electrophysiologic effects of the I(K) (1) inhibitor, PA‐6, are [K+](o)‐dependent

Endometrial BCL6 Overexpression in Eutopic Endometrium of Women With Endometriosis

The objective of this study was to examine B-cell CLL/lymphoma 6 (BCL6) expression in human eutopic endometrium across the menstrual cycle in women with and without endometriosis and to establish a cutoff for future studies. This design was a series of case-control studies in tertiary University teaching hospitals. We examined BCL6 expression by messenger RNA and immunohistochemically in prospectively collected samples in both the proliferative (P) and the secretory phases. BCL6 is minimally increased in the mid-secretory phase of the menstrual cycle compared to the P phase in normal patients. BCL6 protein expression was significantly higher in the secretory phase of patients with endometriosis (n = 29) versus fertile controls without endometriosis at laparoscopy (n = 20; P < .0001). Normal fertile controls (n = 28) recruited for endometrial biopsy also had low levels of secretory phase BCL6 expression compared to women with unexplained infertility (UI; n = 119). A receiving-operator characteristic analysis of these data revealed an area under the curve of 94% (95% confidence interval 85%-100%; P < .0001) with an HSCORE cutoff of 1.4 to differentiate cases with and without endometriosis. Using this cutoff value, BCL6 was positive in 88% of cases with UI. Laparoscopic examination of a subset of 65 patients confirmed abnormalities in 98% of cases; 61 (93.8%) were found to have endometriosis, 3 (4.6%) with hydrosalpinx, and 1 (1.5%) with a normal pelvis. These data suggest that BCL6 is a promising candidate as a single diagnostic biomarker for detection of endometriosis in women with otherwise UI and may be associated with endometrial dysfunction, including progesterone resistanc

Cervical mucus monitoring prevalence and associated fecundability in women trying to conceive

To assess the use of cervical mucus monitoring (CMM) in women trying to conceive and determine whether monitoring is associated with increased cycle-specific probability of conception (fecundability)

Dietary and/or physical activity interventions in women with overweight or obesity prior to fertility treatment : protocol for a systematic review and individual participant data meta-analysis

Funding Information: This project is partly supported by the Centre for Research Excellence in Women's Health in Reproductive Life (app1171592) through a project support grant. RW is supported by a National Health and Medical Research Council (NHRMC) Investigator grant (2009767). LM is supported by a Heart Foundation Future Leader Fellowship. Funding Information: AH reports consultancy for Ferring with respect to the development of a lifestyle app. BWM is supported by an NHMRC Investigator grant (GNT1176437). BWM reports personal fees from ObsEva and Merck, and travel support from Merck, outside the submitted work. RW reports grants from the NHMRC. TM is supported by a Future Leader in Diabetes Award from the European Foundation for the Study of Diabetes/Novo Nordisk Foundation (NNF19SA058975) and grants from the regional health authority in Central Norway. ATK reports personal fees from Merck for lectures. The other authors do not have competing interest to declare. Funding Information: This project is partly supported by the Centre for Research Excellence in Women’s Health in Reproductive Life (app1171592) through a project support grant. RW is supported by a National Health and Medical Research Council (NHRMC) Investigator grant (2009767). LM is supported by a Heart Foundation Future Leader Fellowship. Publisher Copyright: © Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.Peer reviewedPublisher PD

Regulatory Effect of Connexin 43 on Basal Ca2+ Signaling in Rat Ventricular Myocytes

Background: It has been found that gap junction-associated intracellular Ca 2+ [Ca 2+]i disturbance contributes to the arrhythmogenesis and hyperconstriction in diseased heart. However, whether functional gaps are also involved in the regulation of normal Ca 2+ signaling, in particular the basal [Ca 2+] i activities, is unclear. Methods and Results: Global and local Ca 2+ signaling and gap permeability were monitored in cultured neonatal rat ventricular myocytes (NRVMs) and freshly isolated mouse ventricular myocytes by Fluo4/AM and Lucifer yellow (LY), respectively. The results showed that inhibition of gap communication by heptanol, Gap 27 and flufenamic acid or interference of connexin 43 (Cx43) with siRNA led to a significant suppression of LY uptake and, importantly, attenuations of global Ca 2+ transients and local Ca 2+ sparks in monolayer NRVMs and Ca 2+ sparks in adult ventricular myocytes. In contrast, overexpression of rat-Cx43 in NRVMs induced enhancements in the above measurements, and so did in HEK293 cells expressing rat Cx43. Additionally, membrane-permeable inositol 1,4,5-trisphosphate (IP3 butyryloxymethyl ester) and phenylephrine, an agonist of adrenergic receptor, could relieve the inhibited Ca 2+ signal and LY uptake by gap uncouplers, whereas blockade of IP 3 receptor with xestospongin C or 2-aminoethoxydiphenylborate mimicked the effects of gap inhibitors. More importantly, all these gap-associated effects on Ca 2+ signaling were also found in single NRVMs that only have hemichannels instead of gap junctions. Further immunostaining/immunoblotting single myocytes with antibod

Reduced Arrhythmia Inducibility With Calcium/Calmodulin-dependent Protein Kinase II Inhibition in Heart Failure Rabbits.

RationaleCalcium/calmodulin-dependent protein kinase II (CaMKII) is activated in heart failure (HF) and can contribute to arrhythmias induced by β-adrenergic receptor-mediated sarcoplasmic reticulum calcium leak.ObjectiveTo evaluate the effect of CaMKII inhibition on ventricular tachycardia (VT) induction in conscious HF and naive rabbits.Methods and resultsNonischemic HF was induced by aortic insufficiency and constriction. Electrocardiograms were recorded in rabbits pretreated with vehicle (saline) or the CaMKII inhibitor KN-93 (300 μg/kg); VT was induced by infusion of increasing doses of norepinephrine (1.56-25 μg·kg⁻¹·min⁻¹) in naive (n = 8) and HF (n = 7) rabbits. With saline, median VT dose threshold in HF was 6.25 versus 12.5 μg·kg⁻¹·min⁻¹ norepinephrine in naive rabbits (P = 0.06). Pretreatment with KN-93 significantly increased VT threshold in HF and naive rabbits (median = 25 μg·kg⁻¹·min⁻¹, P &lt; 0.05 vs. saline for both groups). Mean cycle length of VT initiation was shorter in HF (221 ± 20 milliseconds) than naive (296 ± 23 milliseconds, P &lt; 0.05) rabbits with saline; this difference was not significant after treatment with KN-93.ConclusionsKN-93 significantly reduced arrhythmia inducibility and slowed initiation of VT, suggesting that CaMKII inhibition may have antiarrhythmic effects in the failing human heart