NADPH oxidase and endoplasmic reticulum stress is associated with neuronal degeneration in orbitofrontal cortex of individuals with alcohol use disorder.

Abstract

Many disorders of the central nervous system (CNS), including alcohol use disorder (AUD), are associated with induction of proinflammatory neuroimmune signalling and neurodegeneration. In previous studies, we found increased expression of Toll-like receptors (TLRs), activated NF-κB p65 (RELA), and other proinflammatory signalling molecules. Proinflammatory NADPH oxidases generate reactive oxygen species, which are linked to neurodegeneration. We tested the hypothesis that AUD increased RELA activation increases NADPH oxidase-oxidative stress and endoplasmic reticulum (ER) stress cell death cascades in association with neuronal cell death in the human orbitofrontal cortex (OFC). In the AUD OFC, we report mRNA induction of several NADPH oxidases, the dual oxidase DUOX2, and the oxidative stress lipid peroxidation marker 4-HNE and the DNA oxidation marker 8-OHdG that correlate with RELA, a marker of proinflammatory NF-κB activation. This was accompanied by increased expression of the ER stress-associated regulator protein glucose-regulated protein 78 (GRP78), transmembrane sensors activating transcription factor 6 (ATF6), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and inositol-requiring kinase/endonuclease 1 (pIRE1), and the pro-apoptotic transcription factor C/EBP homologous protein (CHOP). Expression of NADPH oxidase-oxidative stress markers correlate with ER stress-associated molecules. Induction of oxidative stress and ER stress signalling pathways correlate with expression of cell death-associated caspases and neuronal cell loss. These data support the hypothesis that proinflammatory RELA-mediated induction of NADPH oxidase-oxidative stress and ER stress-associated signalling cascades is associated with neuronal cell death in the post-mortem human OFC of individuals with AUD.