Sustained cardiac hypertrophy represents one of the most common causes leading to cardiac failure. There is emerging evidence to implicate the involvement of NF-B in the development of cardiac hypertrophy. However, several critical questions remain unanswered. We tested the use of soluble epoxide hydrolase (sEH) inhibitors as a means to enhance the biological activities of epoxyeicosatrienoic acids (EETs) to treat cardiac hypertrophy. sEH catalyzes the conversion of EETs to form the corresponding dihydroxyeicosatrienoic acids. Previous data have suggested that EETs may inhibit the activation of NF-B-mediated gene transcription. We directly demonstrate the beneficial effects of several potent sEH inhibitors (sEHIs) in cardiac hypertrophy. Specifically, we show that sEHIs can prevent the development of cardiac hypertrophy using a murine model of pressureinduced cardiac hypertrophy. In addition, sEHIs reverse the preestablished cardiac hypertrophy caused by chronic pressure overload. We further demonstrate that these compounds potently block the NF-B activation in cardiac myocytes. Moreover, by using in vivo electrophysiologic recordings, our study shows a beneficial effect of the compounds in the prevention of cardiac arrhythmias that occur in association with cardiac hypertrophy. We conclude that the use of sEHIs to increase the level of the endogenous lipid epoxides such as EETs may represent a viable and completely unexplored avenue to reduce cardiac hypertrophy by blocking NF-B activation.epoxyeicosatrienoic acids ͉ NF-B

Small conductance Ca2+ -activated K + channels (SK channels) have been reported in excitable cells, where they aid in integrating changes in intracellular Ca 2+ (Ca 2+ i ) with membrane potential. We have recently reported the functional existence of SK2 channels in human and mouse cardiac myocytes. Moreover, we have found that the channel is predominantly expressed in atria compared to the ventricular myocytes. We hypothesize that knockout of SK2 channels may be sufficient to disrupt the intricate balance of the inward and outward currents during repolarization in atrial myocytes. We further predict that knockout of SK2 channels may predispose the atria to tachy-arrhythmias due to the fact that the late phase of the cardiac action potential is highly susceptible to aberrant excitation. We take advantage of a mouse model with genetic knockout of the SK2 channel gene. In vivo and in vitro electrophysiological studies were performed to probe the functional roles of SK2 channels in the heart. Whole-cell patch-clamp techniques show a significant prolongation of the action potential duration prominently in late cardiac repolarization in atrial myocytes from the heterozygous and homozygous null mutant animals. Morover, in vivo electrophysiological recordings show inducible atrial fibrillation in the null mutant mice but not wild-type animals. No ventricular arrhythmias are detected in the null mutant mice or wild-type animals. In summary, our data support the important functional roles of SK2 channels in cardiac repolarization in atrial myocytes. Genetic knockout of the SK2 channels results in the delay in cardiac repolarization and atrial arrhythmias.

Animal models of Zika virus (ZIKV) are needed to better understand tropism and pathogenesis and to test candidate vaccines and therapies to curtail the pandemic. Humans and rhesus macaques possess similar fetal development and placental biology that is not shared between humans and rodents. We inoculated 2 non-pregnant rhesus macaques with a 2015 Brazilian ZIKV strain. Consistent with most human infections, the animals experienced no clinical disease but developed short-lived plasma viremias that cleared as neutralizing antibody developed. In 1 animal, viral RNA (vRNA) could be detected longer in whole blood than in plasma. Despite no major histopathologic changes, many adult tissues contained vRNA 14 days post-infection with highest levels in hemolymphatic tissues. These observations warrant further studies to investigate ZIKV persistence and its potential clinical implications for transmission via blood products or tissue and organ transplants.

Zika virus (ZIKV) infection of pregnant women can cause fetal microcephaly and other neurologic defects. We describe the development of a non-human primate model to better understand fetal pathogenesis. To reliably induce fetal infection at defined times, four pregnant rhesus macaques are inoculated intravenously and intraamniotically with ZIKV at gestational day (GD) 41, 50, 64, or 90, corresponding to first and second trimester of gestation. The GD41-inoculated animal, experiencing fetal death 7 days later, has high virus levels in fetal and placental tissues, implicating ZIKV as cause of death. The other three fetuses are carried to near term and euthanized; while none display gross microcephaly, all show ZIKV RNA in many tissues, especially in the brain, which exhibits calcifications and reduced neural precursor cells. Given that this model consistently recapitulates neurologic defects of human congenital Zika syndrome, it is highly relevant to unravel determinants of fetal neuropathogenesis and to explore interventions.

Abstract-Since the first description of the anatomical atrioventricular nodes (AVNs), a large number of studies have provided insights into the heterogeneity of the structure as well as a repertoire of ion channel proteins that govern this complex conduction pathway between the atria and ventricles. These studies have revealed the intricate organization of multiple nodal and nodal-like myocytes contributing to the unique electrophysiology of the AVN in health and diseases.On the other hand, information regarding the contribution of specific ion channels to the function of the AVN remains incomplete. We reason that the identification of AVN-specific ion channels may provide a more direct and rational design of therapeutic target in the control of AVN conduction in atrial flutter/fibrillation, one of the most common arrhythmias seen clinically. In this study, we took advantage of 2 genetically altered mouse models with overexpression or null mutation of 1 of a small conductance Ca 2ϩ -activated K ϩ channel isoform, SK2 channel, and demonstrated robust phenotypes of AVN dysfunction in these experimental models. Overexpression of SK2 channels results in the shortening of the spontaneous action potentials of the AVN cells and an increase in the firing frequency. On the other hand, ablation of the SK2 channel results in the opposite effects on the spontaneous action potentials of the AVN. Furthermore, we directly documented the expression of SK2 channel in mouse AVN using multiple techniques. The new insights may have important implications in providing novel drug targets for the modification of AVN conduction in the treatment of atrial arrhythmias. Key Words: K Ca 2.2 channel Ⅲ SK2 channel Ⅲ atrioventricular nodes T he atrioventricular node (AVN) is a highly specialized pacemaking tissue located at the junction of the right atrium and ventricle. Indeed, it is the only electrical connection between atria and ventricles and provides the critical delay between atrial and ventricular contraction to allow for proper atrial emptying before the start of the ventricular contraction. Pharmacological slowing of impulses across AVN is widely used clinically in atrial flutter/fibrillation to ensure physiological ventricular responses in these conditions. Previous studies have identified the roles of several distinct ion channels in the AVN function, 1-5 and recent work has begun to assemble an array of ion channel genes in the pacemaking tissues. 6 On the other hand, information regarding contribution of specific ion channels to the function of the AVN remains incomplete. We reason that the identification of AVN-specific ion channels may provide a more direct and rational design of therapeutic target in the control of AVN conduction in atrial flutter/fibrillation, one of the most common arrhythmias seen clinically.Specifically -activated K ϩ channels (SK or K Ca 2). 9 -13 SK channels are encoded by at least 3 distinct genes, namely KCNN1 (SK1), KCNN2 (SK2), and KCNN3 (SK3). 9,10,13 Here, we directly document the robust expres...

Summary Small conductance Ca2+-activated K+ (SK) channels have recently been documented in human and mouse cardiac myocytes that contribute importantly towards cardiac action potential profiles. Three isoforms of SK channel subunits (SK1, 2 and 3) have been demonstrated in the heart. The channels are more prominently expressed in atrial and pacemaking tissues compared to the ventricles. Significance of the channels is underscored by the findings that SK2 channels may play a role in atrial fibrillation. The present study demonstrates the heteromultimerization of different SK channel subunits in human and mouse atrial myocytes. Moreover, the study provides evidence for the direct interaction between the coiled-coil domains in the C-termini of the different SK subunits. Disruption of the coiled-coil domain interaction results in a significant decrease in the Ca2+-activated K+ current in atrial myocytes which is important for cardiac repolarization. Formation of heteromeric channels provides an increase in functional diversity for K+ channels. Moreover, different isoforms of SK channels may represent therapeutic targets to directly modify atrial cells without interfering with ventricular myocytes. Thus, new knowledge into the structure and function of SK channels is important not only from a fundamental viewpoint, but might also have important therapeutic implications in cardiac arrhythmias. Rationale Ca2+-activated K+ channels are present in a wide variety of cells. We have previously reported the presence of small conductance Ca2+-activated K+ (SK or KCa) channels in human and mouse cardiac myocytes that contribute functionally towards the shape and duration of cardiac action potentials. Three isoforms of SK channel subunits (SK1, 2 and 3) are found to be expressed. Moreover, there is differential expression with more abundant SK channels in the atria and pacemaking tissues compared to the ventricles. SK channels are proposed to be assembled as tetramers similar to other K+ channels, but the molecular determinants driving their subunit interaction and assembly are not defined in cardiac tissues. Objective The goal of the study is to investigate the heteromultimeric formation and the domain necessary for the assembly of three SK channel subunits (SK1-3) into complexes in human and mouse hearts. Methods and Results Here, we provide evidence to support the formation of heteromultimeric complexes among different SK channel subunits in native cardiac tissues. SK1, 2 and 3 subunits contain coiled-coil domains (CCDs) in the C-termini. In vitro interaction assay supports the direct interaction between CCDs of the channel subunits. Moreover, specific inhibitory peptides derived from CCDs block the Ca2+-activated K+ current in atrial myocytes which is important for cardiac repolarization. Conclusions The data provide evidence for the formation of heteromultimeric complexes among different SK channel subunits in atrial myocytes. Since SK channels are predominantly expressed in atrial myocytes, specific ligands of th...

The importance of proper ion channel trafficking is underpinned by a number of channel-linked genetic diseases whose defect is associated with failure to reach the cell surface. Conceptually, it is reasonable to suggest that the function of ion channels depends critically on the precise subcellular localization and the number of channel proteins on the cell surface membrane, which is determined jointly by the secretory and endocytic pathways. Yet the precise mechanisms of the entire ion channel trafficking pathway remain unknown. Here, we directly demonstrate that proper membrane localization of a smallconductance Ca 2ϩ -activated K ؉ channel (SK2 or KCa2.2) is dependent on its interacting protein, ␣-actinin2, a major F-actin crosslinking protein. SK2 channel localization on the cell-surface membrane is dynamically regulated, and one of the critical steps includes the process of cytoskeletal anchoring of SK2 channel by its interacting protein, ␣-actinin2, as well as endocytic recycling via early endosome back to the cell membrane. Consequently, alteration of these components of SK2 channel recycling results in profound changes in channel surface expression. The importance of our findings may transcend the area of K ؉ channels, given that similar cytoskeletal interaction and anchoring may be critical for the membrane localization of other ion channels in neurons and other excitable cells.ion channel trafficking ͉ early endosome ͉ cardiac myocytes ͉ small conductance Ca 2ϩ -activated K ϩ channel ͉ calmodulin binding domain T he function of ion channels depends critically on the precise number and subcellular localization of the channel proteins on the cell-surface membrane (1, 2). The steady-state cell-surface expression of ion channels is intricately and dynamically governed by the anterograde (forward) and retrograde trafficking (2, 3). Ion channel molecules are first synthesized in the endoplasmic reticulum (ER), assembled and processed, then trafficked to the membrane where they function. Trafficking of ion channel proteins to the surface membrane involves a series of tightly regulated events coordinated by ER resident proteins, microtubules, transport vesicle and Golgi apparatus, the actin cytoskeleton, myosins, and anchoring proteins (2). The importance of correct ion channel trafficking is highlighted by a number of channel-linked genetic diseases whose defect is associated with failure to reach the cell surface (4-8).Small-conductance Ca 2ϩ -activated K ϩ (SK or K Ca 2) channels belong to a family of Ca 2ϩ -activated K ϩ channels (K Ca ) that have been reported from a wide variety of cells (9-11). SK channels represent a highly unique family of K ϩ channels, in that they are directly gated by changes in intracellular Ca 2ϩ concentration and hence function to integrate changes in Ca 2ϩ concentration with changes in K ϩ conductance and membrane potentials. SK channels have been shown to mediate afterhyperpolarizations in neurons (9, 12, 13) and action potential repolarization in cardiac tissues (14,15). Prev...

SUMMARY Zika virus (ZIKV) causes severe neurologic complications and fetal aberrations. Vaccine development is hindered by potential safety concerns due to antibody cross-reactivity with dengue virus and the possibility of disease enhancement. In contrast, passive administration of anti-ZIKV antibodies engineered to prevent enhancement may be safe and effective. Here, we report on human monoclonal antibody Z021, a potent neutralizer that recognizes an epitope on the lateral ridge of the envelope domain III (EDIII) of ZIKV and is protective against ZIKV in mice. When administered to macaques undergoing a high-dose ZIKV challenge, a single anti-EDIII antibody selected for resistant variants. Co-administration of two antibodies, Z004 and Z021, which target distinct sites on EDIII, was associated with a delay and a 3- to 4-log decrease in peak viremia. Moreover, the combination of these antibodies engineered to avoid enhancement prevented viral escape due to mutation in macaques, a natural host for ZIKV.