Serine/threonine-protein phosphatase 1 α levels are paralleling olfactory memory formation in the CD1 mouse

The epigenetically regulated PP1α expression by KDM1A may contribute to oxycodone conditioned place preference in mice

The lysine-specific demethylase 1 (KDM1A) is reported to be a regulator in learning and memory. However, the effect of KDM1A in oxycodone rewarding memory has yet to be studied. In our study, rewarding memory was assessed by using conditioned place preference (CPP) in male mice. Next generation sequencing and chromatin immunoprecipitation-PCR were used to explore the molecular mechanisms. Oxycodone significantly decreased PP1α mRNA and protein levels in hippocampal neurons. Oxycodone significantly increased KDM1A and H3K4me1 levels, while significantly decreased H3K4me2 levels in a time- and dose-dependent manner. Behavioral data demonstrated that intraperitoneal injection of ORY-1001 (KDM1A inhibitor) or intra-hippocampal injection of KDM1A siRNA/shRNA blocked the acquisition and expression of oxycodone CPP and facilitated the extinction of oxycodone CPP. The decrease of PP1α was markedly blocked by the injection of ORY-1001 or KDM1A siRNA/shRNA. Oxycodone-induced enhanced binding of CoRest with KDM1A and binding of CoRest with the PP1α promoter was blocked by ORY-1001. The level of H3K4me2 demethylation was also decreased by the treatment. The results suggest that oxycodone-induced upregulation of KDM1A via demethylation of H3K4me2 promotes the binding of CoRest with the PP1α promoter, and the subsequent decrease in PP1α expression in hippocampal neurons may contribute to oxycodone reward.

Odour discrimination learning in the Indian greater short-nosed fruit bat (Cynopterus sphinx): differential expression of Egr-1, C-fos and PP-1 in the olfactory bulb, amygdala and hippocampus

Activity-dependent expression of immediate-early genes (IEGs) is induced by exposure to odour. The present study was designed to investigate whether there is differential expression of IEGs (Egr-1, C-fos) in the brain region mediating olfactory memory in the Indian greater short-nosed fruit bat, Cynopterus sphinx We assumed that differential expression of IEGs in different brain regions may orchestrate a preference odour (PO) and aversive odour (AO) memory in C. sphinx We used preferred (0.8% w/w cinnamon powder) and aversive (0.4% w/v citral) odour substances, with freshly prepared chopped apple, to assess the behavioural response and induction of IEGs in the olfactory bulb, hippocampus and amygdala. After experiencing PO and AO, the bats initially responded to both, later only engaging in feeding bouts in response to the PO food. The expression pattern of EGR-1 and c-Fos in the olfactory bulb, hippocampus and amygdala was similar at different time points (15, 30 and 60 min) following the response to PO, but was different for AO. The response to AO elevated the level of c-Fos expression within 30 min and reduced it at 60 min in both the olfactory bulb and the hippocampus, as opposed to the continuous increase noted in the amygdala. In addition, we tested whether an epigenetic mechanism involving protein phosphatase-1 (PP-1) acts on IEG expression. The observed PP-1 expression and the level of unmethylated/methylated promoter revealed that C-fos expression is possibly controlled by odour-mediated regulation of PP-1. These results in turn imply that the differential expression of C-fos in the hippocampus and amygdala may contribute to olfactory learning and memory in C. sphinx.

Perinatal α-linolenic acid availability alters the expression of genes related to memory and to epigenetic machinery, and the Mecp2 DNA methylation in the whole brain of mouse offspring

Many animal and human studies indicated that dietary ω-3 fatty acids could have beneficial roles on brain development, memory, and learning. However, the exact mechanisms involved are far from being clearly understood, especially for α-linolenic acid (ALA), which is the precursor for the ω-3 elongation and desaturation pathways. This study investigated the alterations induced by different intakes of flaxseed oil (containing 50% ALA), during gestation and lactation, upon the expression of genes involved in neurogenesis, memory-related molecular processes, and DNA methylation, in the brains of mouse offspring at the end of lactation (postnatal day 19, P19). In addition, DNA methylation status for the same genes was investigated. Maternal flaxseed oil supplementation during lactation increased the expression of Mecp2, Ppp1cc, and Reelin, while decreasing the expression of Ppp1cb and Dnmt3a. Dnmt1 expression was decreased by postnatal flaxseed oil supplementation but this effect was offset by ALA deficiency during gestation. Mecp2 DNA methylation was decreased by maternal ALA deficiency during gestation, with a more robust effect in the lactation-deficient group. In addition, linear regression analysis revealed positive correlations between Mecp2, Reelin, and Ppp1cc, between Gadd45b, Bdnf, and Creb1, and between Egr1 and Dnmt1, respectively. However, there were no correlations, in any gene, between DNA methylation and gene expression. In summary, the interplay between ALA availability during gestation and lactation differentially altered the expression of genes involved in neurogenesis and memory, in the whole brain of the offspring at the end of lactation. The Mecp2 epigenetic status was correlated with ALA availability during gestation. However, the epigenetic status of the genes investigated was not associated with transcript levels, suggesting that either the regulation of these genes is not necessarily under epigenetic control, or that the whole brain model is not adequate for the exploration of epigenetic regulation in the context of this study.