Background: We previously reported that sevoflurane anesthesia reversibly suppresses the expression of the clock gene
Period2 (Per2)
in the mouse suprachiasmatic nucleus (SCN). However
the molecular mechanisms underlying this suppression remain unclear. In this study
we examined the possibility that sevoflurane suppresses Per2 expression via epigenetic modification of the Per2 promoter.Methods: Mice were anesthetized with a gas mixture of 2.5% sevoflurane/40% oxygen at a 6 L/min flow for 1 or 4 h. After termination
brains were removed and samples of SCN tissue were derived from frozen brain sections. Chromatin immunoprecipitation (ChIP) assays using anti-acetylated-histone antibodies were performed to investigate the effects of sevoflurane on histone acetylation of the Per2 promoter. Interaction between the E'-box (a cis-element in the Per2 promoter) and CLOCK (the Clock gene product) was also assessed by a ChIP assay using an anti-CLOCK antibody. The SCN concentration of nicotinamide adenine dinucleotide (NAD(+))
a CLOCK regulator
was assessed by liquid chromatographymass spectrometry.Results: Acetylation of histone H4 in the proximal region of the Per2 promoter was significantly reduced by sevoflurane. This change in the epigenetic profile of the Per2 gene was observed prior to suppression of Per2 expression. Simultaneously
a reduction in the CLOCK-E'-box interaction in the Per2 promoter was observed. Sevoflurane treatment did not affect the concentration of NAD(+) in the SCN.Conclusions: Independent of NAD(+) concentration in the SCN
sevoflurane decreases CLOCK binding to the Per2 promoter E'-box motif
reducing histone acetylation and leading to suppression of Per2 expression.
