Latent genetic backgrounds and molecular pathogenesis in drug-induced long-QT syndrome.

Abstract

BACKGROUND:

Drugs with I(Kr)-blocking action cause secondary long-QT syndrome. Several cases have been associated with mutations of genes coding cardiac ion channels, but their frequency among patients affected by drug-induced long-QT syndrome (dLQTS) and the resultant molecular effects remain unknown.

METHODS AND RESULTS:

Genetic testing was carried out for long-QT syndrome-related genes in 20 subjects with dLQTS and 176 subjects with congenital long-QT syndrome (cLQTS); electrophysiological characteristics of dLQTS-associated mutations were analyzed using a heterologous expression system with Chinese hamster ovary cells together with a computer simulation model. The positive mutation rate in dLQTS was similar to cLQTS (dLQTS versus cLQTS, 8 of 20 [40%] versus 91 of 176 [52%] subjects, P=0.32). The incidence of mutations was higher in patients with torsades de pointes induced by nonantiarrhythmic drugs than by antiarrhythmic drugs (antiarrhythmic versus others, 3 of 14 [21%] versus 5 of 6 [83%] subjects, P<0.05). When reconstituted in Chinese hamster ovary cells, KCNQ1 and KCNH2 mutant channels showed complex gating defects without dominant negative effects or a relatively mild decreased current density. Drug sensitivity for mutant channels was similar to that of the wild-type channel. With the Luo-Rudy simulation model of action potentials, action potential durations of most mutant channels were between those of wild-type and cLQTS.

CONCLUSIONS:

dLQTS had a similar positive mutation rate compared with cLQTS, whereas the functional changes of these mutations identified in dLQTS were mild. When I(Kr)-blocking agents produce excessive QT prolongation (dLQTS), the underlying genetic background of the dLQTS subject should also be taken into consideration, as would be the case with cLQTS; dLQTS can be regarded as a latent form of long-QT syndrome.

• Authors: Hideki Itoh, Tomoko Sakaguchi, Wei-Guang Ding, Eiichi Watanabe, Ichiro Watanabe, Yukiko Nishio, Takeru Makiyama, Seiko Ohno, Masaharu Akao, Yukei Higashi, Naoko Zenda, Tomoki Kubota, Chikara Mori, Katsunori Okajima, Tetsuya Haruna, Akashi Miyamoto, Mihoko Kawamura, Katsuya Ishida, Iori Nagaoka, Yuko Oka, Yuko Nakazawa, Takenori Yao, Hikari Jo, Yoshihisa Sugimoto, Takashi Ashihara, Hideki Hayashi, Makoto Ito, Keiji Imoto, Hiroshi Matsuura, Minoru Horie
• Journal: Circulation. Arrhythmia and electrophysiology (Circ Arrhythm Electrophysiol) Vol. 2 Issue 5 Pg. 511-23 (Oct 2009) ISSN: 1941-3084 [Electronic] United States
• PMID: 19843919 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• ERG1 Potassium Channel
• Ether-A-Go-Go Potassium Channels
• KCNH2 protein, human
• KCNQ1 Potassium Channel
• Muscle Proteins
• NAV1.5 Voltage-Gated Sodium Channel
• SCN5A protein, human
• Sodium Channels

Topics

• Adult
• Aged
• Animals
• Computer Simulation
• Cricetinae
• DNA Mutational Analysis
• ERG1 Potassium Channel
• Ether-A-Go-Go Potassium Channels (genetics)
• Female
• Genotype
• Humans
• Incidence
• Japan (epidemiology)
• KCNQ1 Potassium Channel (genetics)
• Long QT Syndrome (chemically induced, epidemiology, genetics, physiopathology)
• Male
• Middle Aged
• Muscle Proteins (genetics)
• Mutation, Missense
• NAV1.5 Voltage-Gated Sodium Channel
• Risk Factors
• Sodium Channels (genetics)
• Transfection