Cross sensitization between chronic restraint stress and cocaine: Role of Nuclear Factor kappa B (NF-kB) in Nucleus Accumbens core

SANCHEZ MARIANELA ADELA; MONGI-BRAGATO, BETHANIA; AVALOS MARIA PAULA; GUZMAN ANDREA SUSANA; RIGONI DAIANA; VEDELAGO GEORGINA; BISBAL MARIANO; BOLLATI FLAVIA; CANCELA LILIANA M

Congreso; 3rd FALAN CONGRESS; 2022

Stressful experience induced cross sensitization to cocaine is associated with a significant impairment of glutamate mechanisms in the Nucleus Accumbens core (Nacore). The hallmark of disrupted glutamate homeostasis following restraint stress is the increased basal concentrations of extracellular glutamate attributed to glutamate transporter (GLT-1) downregulation within this brain area. Recent evidence from our lab, demonstrated that microglia, the immunocompetent cells in the brain, play a key role in the proactive influence of stress on impaired glutamate homeostasis in the NAcore. It has been reported a close linkage between glutamate and the activation of the Nuclear Factor-Kappa B (NF-kB). This transcription factor induces the expression of gene targets tightly linked to glia maintenance of glutamate homeostasis, such as GLT-1, and controls the expression of numerous genes involved in inflammation and immune response. Considering these evidences, we hypothesized that the stress-induced disruption of glutamate homeostasis underlying cross-sensitization to cocaine, depends on NF-kB signaling. So, we evaluate the role of NF-kB in NAcore on the long-term expression of restraint stress-induced behavioral cross-sensitization to cocaine. To test this, we used lentiviral vectors DnIKK, that expresses the dominant negative of the IKK activity, and the potent pharmacological inhibitor of NF-kB nuclear translocation, PDTC, to nullify the transcription factor activity. Chronically pre-stressed animals were administered intra-NAcore with DnIKK 7 days, or PDTC 20 minutes before a cocaine challenge administration, respectively. On day 21, behavioral sensitization and the expression of NF-kB and IKKα/β were evaluated. We also determined the GLT1, TNFa, IL6 mRNA levels by qPCR and Western blot. Our results demonstrate that stress induced a marked activation of the canonical NF-kB pathway in the NAcore, determined by increased p65 nuclear levels and of phosphorylation of the cytoplasmic IKKα/β. Consistently, the pharmacological or genetic inhibition of NF-kB activation, was sufficient to prevent stress-induced sensitization to cocaine. Moreover, by DnIKK or PDTC administration, stress-induced GLT-1 downregulation and TNF-alpha elevation in the NAcore were prevented. Thus, this evidence suggests that NF-kB signaling activation would be crucial in the neuroinflammation-dependent imbalance of glutamate mechanisms induced by stress. Furthemore, our results indicate a central role for NF-kB in the long-term neurobiological mechanisms within the Nacore underpinning stress-induced vulnerability to cocaine addiction. All animal experiments were approved by the Animal Care and Use Committee of the Facultad de Ciencias Quimicas (CICUAL), Universidad Nacional de Córdoba (RES HCD 1220/18), which is consistent with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.