Atomoxetine and clock gene expression in human dermal fibroblasts

Introduction Atomoxetine (ATO) is a substrate for ADHD medication. We propose that part of the therapeutic profile of ATO may be through circadian rhythm modulation. The aim of this study was to investigate the clock genes expression in human dermal fibroblasts (HDF) after ATO exposure.

Methods Four healthy controls (HC) participants (3 men, 1 woman; 42.00 ± 15.38 years, mean ± SD) and four volunteers suffering from ADHD (1 man, 3 women; 38.75 ± 8.15 years, mean ± SD) were included in the analysis. All participants completed the Multiple-Choice Word Test (IQ score: HC: 112.25 ± 9.32, mean ± SD; ADHD participants: 110.83 ± 13.27, mean ± SD, n.s), German Morningness-Eveningness-Questionnaire (D-MEQ Score: HC: 50.00 ± 3.74, mean ± SD; ADHD participants: 53.50 ± 9.54, mean ± SD, n.s) and Wender Utah Rating Scale, German short-version (WURSk Score: HC: 13.75 ± 9.98, mean ± SD; ADHD participants: 31.75 ± 6.94, mean ± SD, p = 0.025). HDF were obtained via skin biopsy and cultured under standard conditions (37 °C, 5% CO2). HDF were incubated for 24 hours with 0.20 and 0.58 µM ATO. HDF without ATO incubation were used as negative control (NegControl). After dexamethasone synchronization, sampling was performed every forth hour for a period of 28 hours. CLOCK, BMAL1, CRY1, PER1/2/3 gene expression was measured by qRT-PCR and data was controlled for fitting in a time series model (CircWave). Statistics were calculated using SPSS.

Results ATO (0.58 µM) induced the rhythmicity of CLOCK in ADHD group (p = 0.009, CircWave) whereas this effect was not observed in HC. Moreover, ATO exposure damped the rhythmicity of PER1/2 in ADHD whereas normal rhythmicity of BMAL1, CRY1, PER1/2/3 was observed in HC.

PER1 (ZT4, p = 0.004) and PER2 (ZT8, p = 0.017) differ between HC and ADHD after 0.20 µM ATO exposure. Compared to NegControl, BMAL1 expression differs for ZT0 (p = 0.020) in HC. Similarly, in the ADHD group, 0.20 µM ATO phase shifted the expression of BMAL1 and CRY1 for ZT28 (p = 0.006; p = 0.011). Additionally, 0.58 µM ATO altered the expression of CRY1 (ZT16, p = 0.022) and PER2 (ZT0, p = 0.017) in ADHD. Moreover, PER3 differs for ZT8 (p = 0.015) between the two ATO concentrations.

Conclusion Our results suggest that ATO might influence clock gene expression in HDF. The number of participants will be increased.