Inhibition of IKKβ Reduces Ethanol Consumption in C57BL/6J Mice

Abstract

Proinflammatory pathways in neuronal and non-neuronal cells are implicated in the acute and chronic effects of alcohol exposure in animal models and humans. The nuclear factor-κB (NF-κB) family of DNA transcription factors plays important roles in inflammatory diseases. The kinase IKKβ mediates the phosphorylation and subsequent proteasomal degradation of cytosolic protein inhibitors of NF-κB, leading to activation of NF-κB. The role of IKKβ as a potential regulator of excessive alcohol drinking had not previously been investigated. Based on previous findings that the overactivation of innate immune/inflammatory signaling promotes ethanol consumption, we hypothesized that inhibiting IKKβ would limit/decrease drinking by preventing the activation of NF-κB. We studied the systemic effects of two pharmacological inhibitors of IKKβ, TPCA-1 and sulfasalazine, on ethanol intake using continuous- and limited-access, two-bottle choice drinking tests in C57BL/6J mice. In both tests, TPCA-1 and sulfasalazine reduced ethanol intake and preference without changing total fluid intake or sweet taste preference. A virus expressing Cre recombinase was injected into the nucleus accumbens and central amygdala to selectively knock down IKKβ in mice genetically engineered with a conditional Ikkb deletion (IkkbF/F). Although IKKβ was inhibited to some extent in astrocytes and microglia, neurons were a primary cellular target. Deletion of IKKβ in either brain region reduced ethanol intake and preference in the continuous access two-bottle choice test without altering the preference for sucrose. Pharmacological and genetic inhibition of IKKβ decreased voluntary ethanol consumption, providing initial support for IKKβ as a potential therapeutic target for alcohol abuse.

Gene expression profiling in the human alcoholic brain

“…Ethanol treatment in vivo has been shown to increase the expression of TLRs, resulting in NF-κB activation and cytokine induction (Crews et al, 2013; Lippai et al, 2013). IKKβ regulates activation of NF-κB, and both pharmacologic inhibition and genetic deletion of IKKβ in the nucleus accumbens and central nucleus of the amygdala reduced voluntary alcohol drinking in mice (Truitt et al, 2016), providing further support for NF-κB signaling in chronic drinking. Neurodegeneration caused by chronic alcohol exposure is also partially due to signaling through the TLR and NF-κB signaling pathways (Alfonso-Loeches et al, 2010; Qin et al, 2007).…”

“…Sequence data can be integrated with protein data, physiological function, phenotypic traits, and other factors such as the microbiome, to create a more cohesive picture of the disease state (Farris and Mayfield, 2014). This information, coupled with corresponding information from animal models (Truitt et al, 2016), aims to uncover improved treatment strategies for AUD (Warden et al, 2016), and may one day be used to target an individual’s transcriptome profile. Advances in “precision” and “personalized” medicine could lead to improved therapies that surpass those obtained by current in silico bioinformatics approaches (Shin et al, 2016; Sliwczynski and Orlewska, 2016).…”

“…These studies implicated inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ) as having a modulatory role in alcohol drinking. In a proof-of-concept study, Truitt and colleagues showed that pharmacological and genetic inhibition of IKKβ decreased voluntary ethanol consumption, providing initial support for IKKβ as a potential therapeutic target for alcohol abuse (Truitt et al, 2016), as well as functional evidence that gene network analysis is a viable approach to identify new treatments.…”

Scn4b regulates the hypnotic effects of ethanol and other sedative drugs

“…32,33 These studies provided evidence that gene expression profiling can identify molecular determinants of ethanol drinking and that neuroimmune/inflammatory pathways are relevant targets. 32,33 These studies provided evidence that gene expression profiling can identify molecular determinants of ethanol drinking and that neuroimmune/inflammatory pathways are relevant targets.…”

New Implications for the Melanocortin System in Alcohol Drinking Behavior in Adolescents: The Glial Dysfunction Hypothesis

“…In particular, the ethanol-induced upregulation of iNOS, COX 2 , and IL-1β occurs via the stimulation of RhoE, as well as IRAK and MAP kinases, such as ERK1/2, p-38, and JNK, which trigger the downstream activation of oxidant-sensitive transcription factors NF-κB and AP-1 (Valles et al, 2004; Guasch et al, 2007). Alterations in the expression of pro-inflammatory immune genes occur in postmortem brain from alcoholics and animals exposed to alcohol, whereas molecules known to reduce inflammation have shown to ameliorate alcohol-mediated behaviors in animal models (Mayfield et al, 2013; Cui et al, 2014; Truitt et al, 2016; Nennig and Schank, 2017). Increased free radical production and low antioxidant levels are major features of alcohol-induced brain damage (Crews et al, 2000).…”