Dosing schedule-dependent change in the disruptive effects of interferon-α on the circadian clock function Akiko Shinohara a , Satoru Koyanagi a , Ahmed Mohsen Hamdan a , Naoya Matsunaga a , Hironori Aramaki b , Shigehiro Ohdo a, ⁎ a Pharmaceutics, Division of Clinical Pharmacy, Department of Medico-Pharmaceutical Sciences, Faculty of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-Ku, Fukuoka 812-8582, Japan b Department of Molecular Biology, Daiichi College of Pharmaceutical Sciences, 22-1 Tamagawacho, Minami-ku, Fukuoka 815-8511, Japan abstract article info Article history: Received 9 April 2008 Accepted 15 August 2008 Keywords: Interferon-α Dosing schedule Circadian rhythm Clock genes HepG2 Altered homeostatic regulation, including the disturbance of circadian rhythms, is often observed in patients undergoing interferon (IFN) therapy. We reported previously that IFN-α has the ability to modulate the circadian clock function at the molecular level and that the alteration of clock function could be overcome by changing the dosing schedule. In this study, we investigated the influence of IFN-α on the intrinsic biological rhythms in mice by comparing two dosing schedules, continuous administration and repetitive injection. Continuous administration of IFN-α to mice decreased the rhythm amplitude of locomotor activity, body temperature, leukocyte counts, and plasma corticosterone levels. The treatment also suppressed the oscillation in the expression of clock genes in the liver. On the other hand, modulation effects were scarcely observed in mice treated with repetitive injection of IFN-α. These results indicate that treatment with IFN-α does not always modulate the circadian clock function. This notion was also supported by in vitro findings that the inhibitory action of IFN-α on the expression of clock genes was dependent on its exposure time to cells. The alteration of clock function induced by IFN-α could be avoided by optimizing the dosing schedule. © 2008 Elsevier Inc. All rights reserved. Introduction The mammalian circadian system is hierarchically organized by central and peripheral oscillators. An ensemble of coupled oscillators in the suprachiasmatic nucleus (SCN) of the hypothalamus is entrained to a 24-h period by daily light input from the visual system. Neural and humoral output signals from the SCN coordinate the phase of independent circadian oscillators in peripheral tissues through- out the organism (Kalsbeek et al., 1996; Terazono et al., 2003). Self- sustaining circadian oscillators in the SCN use a molecular mechanism similar to that used in subsidiary oscillators present in all cell types in the organism (Yagita et al., 2001). Recent molecular dissection of the circadian biological clock system has revealed that oscillation in the transcription of specific clock genes plays a central role in the generation of circadian rhythms. Gene products of Clock and Bmal1 form a heterodimer that activates the transcription of Period (Per) and Cryptochrome (Cry) genes. Once PER and CRY proteins have reached a critical concentration, they attenuate CLOCK/BMAL1 transactivation, thereby generating 24-h oscillation in their own transcription (Gekakis et al., 1998; Kume et al., 1999). The clock genes, consisting of a core oscillation loop, control downstream events by regulating the rhythmic expression of clock-controlled genes (Jin et al., 1999; Ripperger et al., 2000; Cheng et al., 2002). The circadian clock system is a fundamental mechanism for adapting to daily variations in environmental conditions. The altered homeostatic regulation, including disturbance of the 24-h rhythm, is implicated in various physiological as well as psychiatric disorders (Winget et al., 1984; Cho et al., 2000). Several drugs can alter the 24-h rhythms of biochemical, physiological, and behavioral processes (Duncan, 1986). The change in rhythmicity is sometimes associated with therapeutic effects (such as with antidepressant drugs) but in other cases may lead to illness and altered homeostatic regulation. Interferons (IFNs), a group of cytokines, have been widely used therapeutically as antiviral and antitumor agents in humans; however, IFNs have various adverse effects on the central nervous system, such as depression and neurosis, and are even reported to sometimes cause suicidal tendencies (Dafny et al., 1985; Baron et al., 1991). We reported previously that IFN-α has the ability to modulate the circadian clock function at the molecular level and that the alteration of clock function could be overcome by changing the dosing schedule (Ohdo et al., 2001; Koyanagi and Ohdo, 2002). In this study, we examined the influence of IFN-α on the intrinsic biological rhythms in mice by comparing two dosing schedules. Mice were treated with either continuous administration or repetitive injection of IFN-α. The mechanism underlying the difference in the disruptive action of IFN-α between the two dosing schedules was Life Sciences 83 (2008) 574–580 ⁎ Corresponding author. Tel.: +8192 642 6610; fax: +81 92 642 6614. E-mail address: ohdo@phar.kyushu-u.ac.jp (S. Ohdo). 0024-3205/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2008.08.005 Contents lists available at ScienceDirect Life Sciences journal homepage: www.elsevier.com/locate/lifescie