Studies On The Effects Of Methadone And Its Isomers On Herg Expressions In Primary Human Cardiomyocytes
Loading...
Date
2016-08
Authors
Hussin, Mohd Farid
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
It has long being recognised that many classes of drugs are associated with risks of cardiotoxicity including QT interval prolongation and cardiac arrhythmia. Of particular concern is methadone, a long-acting opioid agonist widely used nowadays to treat opiate addiction. Despite methadone effectiveness in its intended use, a number of in vitro and in vivo studies have reported side effects ranging from minor to serious adverse event related to the cardiac. In the context of cardiac toxicity, methadone is known to block the human ether-a-go-go related gene (hERG) and cause delay in cardiac repolarisation leading to prolongation of QT interval that predispose patients to life threatening arrhythmia (i.e torsade de pointes). However, whether methadone inhibitory action on hERG extends beyond direct blockage, and involve alterations of hERG gene and protein expression remain unclear. Therefore, in the present study we utilised primary human cardiac myocytes cell culture to examine the effect of methadone on the expression of hERG gene and protein using real-time PCR and Western blotting. Furthermore, the emerging reports on chiral cardiotoxicity of methadone also prompted us to evaluate the impact of individual isomer on the expression of hERG. One single concentration of racemic, (R)-, and (S)-methadone according to published patch-clamp data (IC50) was tested. Effects of these drugs on hERG expression were investigated after 24, 72 and 120 hours treatment. Quantitative real-time PCR (RT-qPCR) result showed that relative mRNA
expression of hERG decreased significantly after 120 hours treatment with racemic and (S)-methadone. The Western blot analysis of hERG protein expression reflected the findings of RT-qPCR for (S)- but not racemic methadone. This observation also applies to (R)-methadone in which neither alteration in the gene nor protein expression was detected with both analyses. Based on the differential expression of hERG gene and protein observed particularly in cells treated with (S)-methadone, we seek to investigate the possible molecular mechanism underlying the inhibitory action of methadone on hERG. Two candidate genes: heat shock protein 90 (Hsp90) and serum/glucocorticoid regulated kinase family (SGK3) were selected and analysed using RT-qPCR. The observed result showed that only SGK3 was affected as evident by small downregulation of the gene at the longest duration of methadone treatment. Overall, in addition to supporting the prior findings with regard to chiral toxicity of methadone, the present study also adds to the knowledge that methadone can pose inhibitory effect on hERG mRNA and protein expression, and it is conceivable to speculate that this may contribute, at least in part to methadone adverse effect on the cardiac.
Description
Keywords
The effects of methadone , in primary human cardiomyocytes.