Role of nucleus accumbens microRNA-181a and MeCP2 in incubation of heroin craving in male rats

Abstract

Rationale Epigenetic regulation has been implicated in the incubation of drug craving (the time-dependent increase in drug seeking after prolonged withdrawal from drug self-administration). There is little information available on the role of microRNAs in incubation of heroin craving. Objective This study aimed to investigate the roles and mechanisms of miR-181a and methyl CpG binding protein 2 (MeCP2) in the nucleus accumbens (NAc) in incubation of heroin seeking. Methods MiRNA sequencing was used to predict potential miRNAs, and miRNA profiles were performed in the NAc after 1 day or 14 days after withdrawal from heroin self-administration. Following 14 days of heroin self-administration, rats were injected of lentiviral vectors into the NAc and evaluated for the effects of overexpression of miR-181a or knockdown of MeCP2 on non-reinforced heroin seeking after 14 withdrawal days. Results Lever presses during the heroin-seeking tests were higher after 14 withdrawal days than after 1 day (incubation of heroin craving). miR-181a expression in NAc was lower after 14 withdrawal days than after 1 day, and meCP2 expression in NAc was higher after 14 days than after 1 day. Luciferase activity assay showed that the 3′UTR of MeCP2 is directly regulated by miR-181a. Overexpression of miR-181a in NAc decreased heroin seeking after 14 withdrawal days and decreased MeCP2 mRNA and protein expression. Knockdown of MeCP2 expression in NAc by LV-siRNA-MeCP2 also decreased heroin seeking after 14 withdrawal days. Conclusions Results indicate that incubation of heroin craving is mediated in part by time-dependent decreases in NAc miR181a expression that leads to time-dependent increases in MeCP2 expression. Our data suggest that NAc miR-181a and MeCP2 contribute to incubation of heroin craving.

Withdrawal: A key consideration in evaluating whether highly processed foods are addictive

“… 24 Animals exhibit craving for a substance by engaging in behavioral indicators that have previously been paired with administration of the substance (e.g., nose pokes and lever presses). 24 , 28 This behavior is also seen when animals are withdrawn from HP foods. When HP foods are removed from the diet, rats exhibit general signs of anhedonia and low overall motivational drive.…”

“…[48][49][50] Like other addictive substances, animal models provide evidence that HP foods or ingredients in these foods (i.e., sugar or fat) can change the reward system in a manner that makes removal of these foods from the diet aversive due to the physical and affective symptoms that emerge. 51 Neural reward changes in response to HP food withdrawal are particularly salient for adolescent rodents due to T A B L E 2 Current animal model evidence for HP food withdrawal Animals express physical indicators of withdrawal during HP food withdrawal 22,23 Animals display affective indicators of withdrawal during HP food withdrawal 24,25 Animals show neural reward dysfunction during HP food withdrawal [22][23][24][25][26][27][28] Animals show increased CRF expression during HP food withdrawal 29 Animals show enhanced motivational drive/craving to consume HP food during HP food withdrawal 26,30,31 Animals show increased binge eating behavior during HP food withdrawal 28 higher cortical and subcortical concentrations of dopamine during this stage. 52 Importantly, animals only demonstrate withdrawal-like symptoms after exposure to HP food and not following consumption of less rewarding, more nutritious foods like standard chow.…”

“…Another core component of withdrawal demonstrated by animal models is enhanced motivational drive to consume the substance, which can also be conceptualized as craving 24 . Animals exhibit craving for a substance by engaging in behavioral indicators that have previously been paired with administration of the substance (e.g., nose pokes and lever presses) 24,28 . This behavior is also seen when animals are withdrawn from HP foods.…”

Orbitofrontal cortex microRNAs support long-lasting heroin seeking behavior in male rats

“…Other studies have demonstrated that miRNA signaling in the NAc can impact opioid self-administration behavior. Overexpression of miR-181 in the NAc of heroin SA rats decreased heroin seeking after 14D of forced abstinence [ 61 ]. Similarly, NAc miR-218 inhibited heroin-induced reinforcement in both conditioned placed preference and self-administration [ 55 , 61 ].…”

Epigenetic Effects of Addictive Drugs in the Nucleus Accumbens

“…For example, long ncRNAs can be regulated by cocaine at least 24 hrs after the last injection ( Bu et al, 2012 ). Also, microRNAs are regulated by cocaine, heroin, and methamphetamine in the NAc ( Eipper-Mains et al, 2011 ; Su et al, 2019 ; Dash et al, 2020 ; Yang et al, 2020 ; Li et al, 2021 ; Xu et al, 2021 ) and the dorsal striatum ( Hollander et al, 2010 ; Im et al, 2010 ). Finally, small nucleolar RNAs (snoRNAs) are also regulated by cocaine and knockdown of MBII-52 attenuates cocaine CPP ( Chen et al, 2014 ).…”