Age-related differences in anxiety-like behavior and amygdalar CCL2 responsiveness to stress following alcohol withdrawal in male Wistar rats

Abstract

Rationale Behavioral and neuroimmune vulnerability to withdrawal from chronic alcohol varies with age. The relation of anxiety-like behavior to amygdalar CCL2 responses following stress after withdrawal from chronic intermittent alcohol (CIA) was investigated in adolescent and adult rats. Methods Adolescent and adult Wistar rats were exposed to CIA (three 5-day blocks of dietary alcohol separated by 2 days of withdrawal) at concentrations that created similar blood alcohol levels across age. Twenty-four hours into the final withdrawal, half of the rats were exposed to 1 h of restraint stress. Four hours post-stress, rats were used for behavior or tissue assays. Results Anxiety-like behavior was increased versus controls by CIA in adolescents and by CIA + stress in adults. CCL2 mRNA was increased versus controls by CIA in adolescents and by CIA and CIA + stress in adults. CCL2 co-localization with neuronal marker NeuN was decreased versus controls by CIA in adolescents and by CIA + stress in adults. CCL2 co-localization with astrocytic marker GFAP was decreased versus controls by CIA and CIA + stress in adolescents, but experimental groups did not differ from controls in adults. CCL2 co-localization with microglial marker Iba1 was decreased versus controls by stress alone in adolescents and by CIA + stress in adults. Conclusions Changes in CCL2 protein might control behavior at either age but are particularly associated with CIA alone in adolescents and with CIA + stress in adults. That the number of CeA neurons expressing CCL2 was altered after CIA and stress is consistent with CCL2 involvement in neural function.

Role of MCP-1 and CCR2 in ethanol-induced neuroinflammation and neurodegeneration in the developing brain

“…For example, it is shown that MCP-1/CCR2 signaling regulates voluntary ethanol consumption. MCP-1 is also involved in ethanol-induced anxiety-like behavior in adolescent rats [ 82 ]. The current finding along with our recent study [ 70 ] add that MCP-1/CCR2-mediated neuroinflammation and microglial activation contribute to ethanol neurotoxicity in the developing CNS.…”

Phenotyping CCL2 Containing Central Amygdala Neurons Controlling Alcohol Withdrawal-Induced Anxiety

“…Given that chemokines like CCL2 are thought to act as neuromodulators (Adler et al, 2006;Gruol, 2016), it has been suggested that CCL2 and similar chemokines can alter alcohol withdrawal-related behaviors. CCL2 has been linked to important alcohol-related behaviors, drinking (Blednov et al, 2005;June et al, 2015;Valenta and Gonzales, 2016), and alcohol withdrawal-induced anxiety-like behavior (Knapp et al, 2011;Harper et al, 2017) making it an important candidate target for the treatment of alcohol use disorder. The balance between pro-inflammatory chemokines like CCL2 and anti-inflammatory chemokines like fractalkine (CX3CL1) seems to be important to behavioral output such as alcohol drinking with CCL2 promoting drinking behavior while CX3CL1 inhibits drinking behavior (Aurelian and Balan, 2019).…”

“…CCL2 is expressed in neurons, microglia, and astrocytes (Banisadr et al, 2005a;June et al, 2015;Harper et al, 2017), and most studies to date have looked at expression changes caused by alcohol in tissues containing all three cell types. With few exceptions (Gruol, 2016;Harper et al, 2017), most of the studies examined the effect of altered CCL2 expression on behavior in a non-cell type-specific manner. In the amygdala, changes in CCL2 were shown to occur as early as 5 h into alcohol withdrawal (Harper et al, 2017(Harper et al, , 2018.…”

“…With few exceptions (Gruol, 2016;Harper et al, 2017), most of the studies examined the effect of altered CCL2 expression on behavior in a non-cell type-specific manner. In the amygdala, changes in CCL2 were shown to occur as early as 5 h into alcohol withdrawal (Harper et al, 2017(Harper et al, , 2018. The central nucleus of the amygdala (CeA) has been shown to have changes in both CCL2 mRNA (Freeman et al, 2012) and the number of neurons containing CCL2 during alcohol withdrawal (Harper et al, 2017).…”

A Rationale for Allopregnanolone Treatment of Alcohol Use Disorders: Basic and Clinical Studies

“…EtOH activates the TLR‐MyD88‐NFκB pathways as well as the TLR3‐regulated TRIF‐pathway. Intermittent alcohol drinking during adolescence upregulates the expression of TLR4 in the adult hippocampus, TLR3 and TLR4 in the adult prefrontal cortex, and TLR1‐TLR8 in the adult cerebellum of male rats (Breese and Knapp, ; Harper et al, ; Knapp et al, ), suggesting distinct immune activation and function at distinct brain sites. Production of proinflammatory cytokines appears to be involved in the altered brain activity associated with alcohol intoxication and dependence (Gruol, ).…”