Pre-reproductive stress and fluoxetine treatment in rats affect offspring A-to-I RNA editing, gene expression and social behavior

Abstract

Adenosine to inosine RNA editing is an epigenetic process that entails site-specific modifications in double-stranded RNA molecules, catalyzed by adenosine deaminases acting on RNA (ADARs). Using the multiplex microfluidic PCR and deep sequencing technique, we recently showed that exposing adolescent female rats to chronic unpredictable stress before reproduction affects editing in the prefrontal cortex and amygdala of their newborn offspring, particularly at the serotonin receptor 5-HT2c (encoded by Htr2c). Here, we used the same technique to determine whether post-stress, pre-reproductive maternal treatment with fluoxetine (5 mg/kg, 7 days) reverses the effects of stress on editing. We also examined the mRNA expression of ADAR enzymes in these regions, and asked whether social behavior in adult offspring would be altered by maternal exposure to stress and/or fluoxetine. Maternal treatment with fluoxetine altered Htr2c editing in offspring amygdala at birth, enhanced the expression of Htr2c mRNA and RNA editing enzymes in the prefrontal cortex, and reversed the effects of pre-reproductive stress on Htr2c editing in this region. Furthermore, maternal fluoxetine treatment enhanced differences in editing of glutamate receptors between offspring of control and stress-exposed rats, and led to enhanced social preference in adult offspring. Our findings indicate that pre-gestational fluoxetine treatment affects patterns of RNA editing and editing enzyme expression in neonatal offspring brain in a region-specific manner, in interaction with pre-reproductive stress. Overall, these findings imply that fluoxetine treatment affects serotonergic signaling in offspring brain even when treatment is discontinued before gestation, and its effects may depend upon prior exposure to stress.

Pre-reproductive stress in adolescent female rats alters oocyte microRNA expression and offspring phenotypes: pharmacological interventions and putative mechanisms

“…Some of the behavioral and molecular findings in adult rats agree with our previous findings 28 , 29 , 49 , 71 , while others differ. This may be due to differences in the order and identity of the behavioral assays, which could have affected behavioral and, well as, gene expression profiles.…”

Gestational Factors throughout Fetal Neurodevelopment: The Serotonin Link

“…The HPA-axis is a brain circuitry, which is mainly affected by gestational SSRI intake studied in the offspring from stressed dams. Alterations have been related to the earlier discussed increases in anxiety-like behavior (probably via increased 5-HT 2C receptor gene expression in the PFC and amygdala) and enhanced social preference [213,232]. While prenatal fluoxetine in healthy dams reduced stress-induced plasma corticosterone levels in adult male offspring, neonatal fluoxetine in healthy dams increased these levels in the serum of adult male offspring.…”

“…Bond et al [227] Maloney et al [226] (social preference) Ehrlich et al [218] Khatri et al [205] Olivier et al [209] Rodriguez-Porcel et al [228] Simpson et al [229] Silva et al [222] Yu et al [223] Zimmerberg & Germeyan [224] Houwing et al [230] Gemmel et al [150] (normalised stress effect) Gemmel et al [160] (irrespective of stress effect) Ko et al [206] Maloney et al [226] (social interaction) Meyer et al [221] Svirsky et al [231] Zaidan et al [232] A few studies investigated the effects of gestational SSRI exposure on the 5-HT system of the offspring. Offspring of pregnant mice that were perinatally treated with fluoxetine and sertraline or prenatally with escitalopram exhibited whole brain decreases in MAOA expression and whole brain increases in cortical expression of TPH2, 5-HTT, and 5-HT 1A/2A/C receptors [218,221,227].…”

“…Lastly, pregestational fluoxetine exposure affected 5-HT 2C receptor gene expression and editing in neonatal amygdala and PFC. Maternal restraint stress prior to pregestational fluoxetine administration revealed that fluoxetine exposure can either reverse or enhance 5-HT 2C receptor editing in the neonatal PFC [232].…”

RNA Editing and Modifications in Mood Disorders

“…Intriguingly, in rats, maternal treatment with fluoxetine reduced 5-HT2c-R editing in the amygdala of the offspring at birth (out of 146 sites analysed), upregulated the expression of 5-HT2c-R mRNA and ADAR enzymes in PFC and rescued pre-reproductive stress modifications on 5-HT2c-R editing in the same region. Furthermore, maternal treatment with fluoxetine increased alterations of glutamate receptors editing levels between offspring of stress-exposed rats and their controls, leading to enhanced social preference in adult offspring [75].…”