Dysregulated circadian functions contribute to various diseases, including
cardiovascular disease. Much progress has been made on chronotherapeutic applications of drugs against
cardiovascular disease (CVD); however, the direct effects of various medications on the circadian system are not well characterized. We previously conducted high-throughput chemical screening for clock modulators and identified an off-patent
anti-arrhythmic drug,
moricizine, as a clock-period lengthening compound. In Per2:LucSV reporter fibroblast cells, we showed that under both
dexamethasone and
forskolin synchronization,
moricizine was able to increase the circadian period length, with greater effects seen with the former. Titration studies revealed a dose-dependent effect of
moricizine to lengthen the period. In contrast,
flecainide, another Class I
anti-arrhythmic, showed no effects on circadian reporter rhythms. Real-time qPCR analysis in fibroblast cells treated with
moricizine revealed significant circadian time- and/or treatment-dependent expression changes in core clock genes, consistent with the above period-lengthening effects. Several clock-controlled cardiac channel genes also displayed altered expression patterns. Using tissue explant culture, we showed that
moricizine was able to significantly prolong the period length of circadian reporter rhythms in atrial ex vivo cultures. Using wild-type C57BL/6J mice,
moricizine treatment was found to promote sleep, alter circadian gene expression in the heart, and show a slight trend of increasing free-running periods. Together, these observations demonstrate novel clock-modulating activities of
moricizine, particularly the period-lengthening effects on cellular oscillators, which may have clinical relevance against
heart diseases.