Period2 gene regulates diurnal changes of nasal symptoms in an allergic rhinitis mouse model

Allergic rhinitis (AR) symptoms exhibit prominent 24-hour variations associated with the biological clock. Although endogenous glucocorticoids synchronize circadian oscillator in the nasal mucosa, the precise mechanism of AR remains unclear. Therefore, using a mouse model, we investigated the association between circadian-clock genes and AR symptoms at various time-points.

Based on the rhythmic secretion of corticosterone levels, we chose 2 time-points, ZT4 (10:00 AM) and ZT16 (10:00 PM), to observe dynamic changes of nasal symptoms, immunologic responses, and circadian-clock gene period (Per) expressions.

In the AR group, nasal symptom scores at ZT4 were significantly higher than at ZT16, with a greater increase in eosinophils, mast cells, and total immunoglobulin E levels at ZT4. The scores had a negative correlation with fluctuation of corticosterone levels. T-helper 1 (Th1) cell counts and interferon-γ levels decreased significantly at ZT4 compared with ZT16 in the AR group, whereas Th2 cells; Th17 cells; and interleukin (IL)-4, -13, and -17A levels increased significantly at ZT4 compared with ZT16. Furthermore, Per2 gene expression levels were attenuated at ZT4 and elevated at ZT16, but correlated negatively with Th2 and Th17 responses associated with Gata3 and Rorγt expression levels that were enhanced at ZT4 and reduced at ZT16 in the AR group.

Our results suggest that the Per2 gene may influence diurnal variations of AR symptom severity, partially through its possible anti-inflammatory effect on the circadian regulation of GATA3 and RORγt levels in immune cells. This further demonstrates the neural-immune-endocrinal mechanism of circadian rhythm in AR and sheds new light on chronotherapeutic approaches to AR.