Impact of melatonin on gene expression in colonic epithelium of pinealectomized rats. Rattus norvegicus

To examine the effect of melatonin on global gene expression in the colonic epithelium, we used RNA-seq analysis to identify differentially expressed genes (DEGs) in samples from three melatonin-treated (MEL4-6) versus three vehicle-treated pinealectomized rats (VEH1-3) injected i.p. at the beginning of subjective night and sacrificed 4 h later. More than 12 050 expressed genes were identified in each sample out of 18 258 genes in the database. A surprisingly small number of significant DEGs (49) was identified. The GO pathways analysis revealed that the largest group of the DEGs was associated with immune system response. Most DEGs (47) identified by RNA-seq were independently analyzed by RT-qPCR and the correlation between both methods indicates reliability of the data. Overall design: To avoid a potential masking effect of endogenous pineal melatonin rhythm, we performed the study on six pinealectomized adult male Wistar rats. We injected the animals i.p. with either melatonin (MEL, 1mg/kg of body weight, n = 3) or vehicle (VEH, 2.5% ethanol in PBS, n = 3) solution at the beginning of subjective night, sacrificed them 4 h later, isolated total RNA from the colonic inner epithelial layer and subjected the samples to RNA-seq differential expression analysis on HiSeq 4000 (Illumina) by BGI International (Shenzhen, China).