Background and purpose: Many drugs associated with acquired long QT syndrome (LQTS) directly block human ether-a-gogo-related gene (hERG) K þ channels. Recently, disrupted trafficking of the hERG channel protein was proposed as a new mechanism underlying LQTS, but whether this defect coexists with the hERG current block remains unclear. This study investigated how ketoconazole, a direct hERG current inhibitor, affects the trafficking of hERG channel protein.Experimental approach: Wild-type hERG and SCN5A/hNa v 1.5 Na þ channels or the Y652A and F656C mutated forms of the hERG were stably expressed in HEK293 cells. The K þ and Na þ currents were recorded in these cells by using the whole-cell patch-clamp technique (231C). Protein trafficking of the hERG was evaluated by Western blot analysis and flow cytometry. Key results: Ketoconazole directly blocked the hERG channel current and reduced the amount of hERG channel protein trafficked to the cell surface in a concentration-dependent manner. Current density of the hERG channels but not of the hNa v 1.5 channels was reduced after 48 h of incubation with ketoconazole, with preservation of the acute direct effect on hERG current. Mutations in drug-binding sites (F656C or Y652A) of the hERG channel significantly attenuated the hERG current blockade by ketoconazole, but did not affect the disruption of trafficking. Conclusions and implications: Our findings indicate that ketoconazole might cause acquired LQTS via a direct inhibition of current through the hERG channel and by disrupting hERG protein trafficking within therapeutic concentrations. These findings should be considered when evaluating new drugs.

1 b-Blockers are widely used in the treatment of cardiovascular diseases. However, their effects on HERG channels at comparable conditions remain to be defined. We investigated the direct acute effects of b-blockers on HERG current and the molecular basis of drug binding to HERG channels with mutations of putative common binding site (Y652A and F656C). 2 b-Blockers were selected based on the receptor subtype. Wild-type, Y652A and F656C mutants of HERG channel were stably expressed in HEK293 cells, and the current was recorded by using wholecell patch-clamp technique (231C). 3 Carvedilol (nonselective), propranolol (nonselective) and ICI 118551 (b 2 -selective) inhibited HERG current in a concentration-dependent manner (IC 50 0.51, 3.9 and 9.2 mM, respectively). The IC 50 value for carvedilol was a clinically relevant concentration. High metoprolol (b 1 -selective) concentrations were required for blockade (IC 50 145 mM), and atenolol (b 1 -selective) did not inhibit the HERG current. 4 Inhibition of HERG current by carvedilol, propranolol and ICI 118551 was partially but significantly attenuated in Y652A and F656C mutant channels. Affinities of metoprolol to Y652A and F656C mutant channels were not different compared with the wild-type. 5 HERG current block by all b-blockers was not frequency-dependent. 6 Drug affinities to HERG channels were different in b-blockers. Our results provide additional strategies for clinical usage of b-blockers. Atenolol and metoprolol may be preferable for patients with type 1 and 2 long QT syndrome. Carvedilol has a class III antiarrhythmic effect, which may provide the rationale for a favourable clinical outcome compared with other b-blockers as suggested in the recent COMET (Carvedilol Or Metoprolol European Trial) substudy.

Aims-In the type 3 long QT syndrome (LQT3), shortening of the QT interval by overdrive pacing is used to prevent life-threatening arrhythmias. However, it is unclear whether accelerated heart rate induced by β-adrenergic agents produces similar effects on the late sodium current (I Na ) to those by overdrive pacing therapy. We analyzed the β-adrenergic-like effects of protein kinase A and fluoride on I Na in R1623Q mutant channels.Main methods-cDNA encoding either wild-type (WT) or R1623Q mutant of hNa v 1.5 was stably transfected into HEK293 cells. I Na was recorded using a whole-cell patch-clamp technique at 23 °C .Key findings-In R1623Q channels, 2 mM pCPT-AMP and 120 mM fluoride significantly delayed macroscopic current decay and increased relative amplitude of the late I Na in a time-dependent manner. Modulations of peak I Na gating kinetics (activation, inactivation, recovery from inactivation) by fluoride were similar in WT and R1623Q channels. The effects of fluoride were almost completely abolished by concomitant dialysis with a protein kinase inhibitor. We also compared the effect of pacing with that of β-adrenergic stimulation by analyzing the frequency-dependence of the late I Na . Fluoride augmented frequency-dependent reduction of the late I Na , which was due to preferential delay of recovery of late I Na . However, the increase in late I Na by fluoride at steady-state was more potent than the frequency-dependent reduction of late I Na .Significance-Different basic mechanisms participate in the QT interval shortening by pacing and β-adrenergic stimulation in the LQT3.

A 33-year-old female was admitted to a hospital with chief complaints of abdominal pain, fever, cough and migrating subcutaneous induration. She had consumed half-cooked crabs 3 months ago. On admission, a mass in the abdominal wall, pleural effusion, a nodular shadow in the right upper lung on the chest X-ray and multiple low density areas in the liver on CT. Peripheral blood examination disclosed marked eosinophilia (5,300/mm3). Although we failed to detect any parasite eggs in stool, sputum and bronchogenic secretion, the immuno-serological test for parasites revealed an infection of paragonimus. Oral administration of praziquantel resulted in the disappearance of nodular shadow in the right upper lung, multiple low density areas on CT as well as migrating subcutaneous indurations. Migration of Paragonimus westermanii larvae to liver is known to be uncommon. Thus, the present case indicates an alternate migration route of the Paragonimus westermanii in humans.

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