Background-Antiarrhythmic management of atrial fibrillation (AF) remains a major clinical challenge. Mechanismbased approaches to AF therapy are sought to increase effectiveness and to provide individualized patient care. K 2P 3.1 (TASK-1 [tandem of P domains in a weak inward-rectifying K + channel-related acid-sensitive K + channel-1]) 2-poredomain K + (K 2P ) channels have been implicated in action potential regulation in animal models. However, their role in the pathophysiology and treatment of paroxysmal and chronic patients with AF is unknown. Methods and Results-Right and left atrial tissue was obtained from patients with paroxysmal or chronic AF and from control subjects in sinus rhythm. Ion channel expression was analyzed by quantitative real-time polymerase chain reaction and Western blot. Membrane currents and action potentials were recorded using voltage-and current-clamp techniques. K 2P 3.1 subunits exhibited predominantly atrial expression, and atrial K 2P 3.1 transcript levels were highest among functional K 2P channels. K 2P 3.1 mRNA and protein levels were increased in chronic AF. Enhancement of corresponding currents in the right atrium resulted in shortened action potential duration at 90% of repolarization (APD 90 ) compared with patients in sinus rhythm. In contrast, K 2P 3.1 expression was not significantly affected in subjects with paroxysmal AF. Pharmacological K 2P 3.1 inhibition prolonged APD 90 in atrial myocytes from patients with chronic AF to values observed among control subjects in sinus rhythm. Conclusions-Enhancement of atrium-selective K 2P 3.1 currents contributes to APD shortening in patients with chronic AF, and K 2P 3.1 channel inhibition reverses AF-related APD shortening. These results highlight the potential of K 2P 3.1 as a novel drug target for mechanism-based AF therapy.

+ , Ca 2+, or other K + currents. Whole-cell SK current sensitive to NS8593 was significantly larger in pulmonary vein (PV) versus left atrial (LA) cells, without a difference in SK single-channel open probability (P o ), whereas AT-P enhanced both whole-cell SK currents and single-channel P o . SK-current block increased action potential duration in both PV and LA cells after AT-P; but only in PV cells in absence of AT-P. SK2 expression was more abundant at both mRNA and protein levels for PV versus LA in control dogs, in both control and AT-P; AT-P upregulated only SK1 at the protein level. Intravenous administration of NS8593 (5 mg/kg) significantly prolonged atrial refractoriness and reduced AF duration without affecting the Wenckebach cycle length, left ventricular refractoriness, or blood pressure. Conclusions-SK

No abstract

Voltage-gated Kv1.1 channels encoded by the Kcna1 gene are traditionally regarded as being neural-specific with no known expression or intrinsic functional role in the heart. However, recent studies in mice reveal low-level Kv1.1 expression in heart and cardiac abnormalities associated with Kv1.1-deficiency suggesting that the channel may have a previously unrecognized cardiac role. Therefore, this study tests the hypothesis that Kv1.1 channels are associated with arrhythmogenesis and contribute to intrinsic cardiac function. In intra-atrial burst pacing experiments, Kcna1-null mice exhibited increased susceptibility to atrial fibrillation (AF). The atria of Kcna1-null mice showed minimal Kv1 family ion channel remodeling and fibrosis as measured by qRT-PCR and Masson’s trichrome histology, respectively. Using RT-PCR, immunocytochemistry, and immunoblotting, KCNA1 mRNA and protein were detected in isolated mouse cardiomyocytes and human atria for the first time. Patients with chronic AF (cAF) showed no changes in KCNA1 mRNA levels relative to controls; however, they exhibited increases in atrial Kv1.1 protein levels, not seen in paroxysmal AF patients. Patch-clamp recordings of isolated human atrial myocytes revealed significant dendrotoxin-K (DTX-K)-sensitive outward current components that were significantly increased in cAF patients, reflecting a contribution by Kv1.1 channels. The concomitant increases in Kv1.1 protein and DTX-K-sensitive currents in atria of cAF patients suggest that the channel contributes to the pathological mechanisms of persistent AF. These findings provide evidence of an intrinsic cardiac role of Kv1.1 channels and indicate that they may contribute to atrial repolarization and AF susceptibility.

No abstract

Cellulose nanofibrils (CNFs) have attracted great attention because of their unique mechanical and optical properties for a variety of applications in composites, packaging materials, and electronics. Green, low-cost, and sustainable production of CNFs, however, is still challenging. Herein, an economic system using a type of a recyclable solid organic acid, maleic acid (MA), was developed to prepare carboxylated CNFs from bleached pulp fibers. The physical and chemical properties of the CNF can be tailored by adjusting the acid hydrolysis intensity or combined hydrolysis factor. Because of its low water solubility, MA can be easily recovered with a yield of approximately 90% after hydrolysis reactions through simple crystallization technology. The recyclability experiment of MA showed that the recovery yield of the acid was still 84% in the fourth cycle and the chemical structure of the recycled MA was almost unchanged throughout the recycling cycles. More importantly, the hydrolysis efficiency was not decreased after the recycling process, thereby endowing the resulting CNF with stable performance. Overall, this work provides a green and economically feasible method to recover and reuse MA for sustainable and large-scale production of CNFs.

No abstract

No abstract