Adenosinergic Regulation of Striatal Clock Gene Expression and Ethanol Intake During Constant Light

Abstract

Circadian rhythm and sleep disruptions occur frequently in individuals with alcohol use disorders (AUD) and present significant barriers to treatment. Recently, a variant of adenosine transporter, equilibrative nucleoside transporter 1 (ENT1), was associated with the cooccurrence of sleep problems and AUD. We have previously shown that mice lacking ENT1 (ENT1 KO) have reduced adenosine levels in the striatum and drink more alcohol compared with wild types (WT). However, it is unknown whether ENT1 deletion disrupts circadian rhythms, which may contribute to alcohol preference in ENT1 KO mice. Here we used these mice to determine whether endogenous adenosine regulates circadian genetic and behavioral rhythms and influences alcohol intake during chronodisruption. We examined circadian locomotor activity in ENT1 KO vs WT littermates and found that ENT1 KO mice were both active earlier and hyperactive compared with WT mice at night. We used real-time PCR and immunohistochemistry to estimate striatal clock gene levels and found that PER2 expression in the striatum was blunted by ENT1 deletion or A2A receptor (A2AR) antagonism. Next, we exposed ENT1 KO and WT mice to constant light (LL) and found further elevation in ethanol intake in ENT1 KO, but not in WT mice, supporting the notion that circadian dysfunction may contribute to increased alcohol intake in ENT1 KO mice. Finally, we showed that A2AR agonist administration normalized PER1 and PER2 expression and circadian locomotor activity in ENT1 KO mice. Together, our results demonstrate that adenosine signaling regulates cellular and behavioral circadian timing and influences alcohol intake during chronodisruption.

Purinergic Signaling in Neuron-Astrocyte Interactions, Circadian Rhythms, and Alcohol Use Disorder

“…Interestingly, levels of extracellular adenosine peak early during circadian nighttime and progressively increase throughout the course of the circadian day (Porkka-Heiskanen et al, 1997 ). This circadian rhythm is synchronized with the cyclic expression of transporters responsible for regulating synaptic adenosine, including ENT1 (Ruby et al, 2014b ). Interestingly, disruption of ENT1 function via genetic knockout reduces synaptic adenosine concentrations and lowers the peak expression of clock genes, including Per2 (Ruby et al, 2014b ).…”

“…This circadian rhythm is synchronized with the cyclic expression of transporters responsible for regulating synaptic adenosine, including ENT1 (Ruby et al, 2014b ). Interestingly, disruption of ENT1 function via genetic knockout reduces synaptic adenosine concentrations and lowers the peak expression of clock genes, including Per2 (Ruby et al, 2014b ). Furthermore, ENT1 KO mice display altered circadian rhythms marked by early onset of an elongated and hyperactive active phase (Ruby et al, 2014b ).…”

“…Interestingly, disruption of ENT1 function via genetic knockout reduces synaptic adenosine concentrations and lowers the peak expression of clock genes, including Per2 (Ruby et al, 2014b ). Furthermore, ENT1 KO mice display altered circadian rhythms marked by early onset of an elongated and hyperactive active phase (Ruby et al, 2014b ). Similar circadian disruptions are also induced by caffeine and A2AR antagonism, which lengthen the period of molecular clock oscillations and induce behavioral changes in the sleep-wake cycle (Antle et al, 2001 ; Burke et al, 2015 ).…”

Sleep-Wake Regulation and Its Impact on Working Memory Performance: The Role of Adenosine

“…Similarly, there is first evidence that adenosine might exert an influence on the circadian clockwork. It has been shown that A 2A receptor antagonism and knock-out of an equilibrative adenosine transporter (equilibrative nucleoside transporter 1 [ENT1]) is linked to blunted Per2 expression in the striatum, but not in the SCN [ 99 ]. Yet, to our knowledge, a direct link between the sleep-homeostatic regulation of adenosine ( i.e.…”

Genes and Alcohol Consumption

“…Chen et al, 2010; Choi et al, 2004; M. R. Lee et al, 2013; Nam, Hinton, et al, 2013; Nam et al, 2011; Ruby et al, 2014; Ruby, Walker, An, Kim, & Choi, 2011). Thus, studies from multiple labs support a role for adenosine in controlling alcohol-seeking behavior.…”