Alcohol (ethanol, EtOH) is among the top ten most addictive substances and has been consumed globally for centuries [1]. The harmful use of alcohol results in a substantial disease burden and leads to significant social and economic losses [2,3]. It is well-established that excessive and chronic alcohol consumption can lead to various cognitive deficits, including impairments in memory, attention and executive function [4,5]. Individuals with alcohol-related cognitive impairment tend to exhibit poorer treatment adherence and reduced self-efficacy, leading to increased alcohol consumption [6]. Recently, excessive alcohol consumption has been identified as a risk factor for the development of dementia [7]. Microglial inflammation is a hallmark of alcohol-related cognitive impairment [8,9]. Alcohol induces mitochondrial damage and reactive oxygen species (ROS) production in microglia, triggering activation of the NOD-like receptor protein 3 (NLRP3) inflammasome and subsequent secretion of IL-1β [[10], [11], [12], [13]]. The mPFC, which plays a key role in cognition, is highly vulnerable to alcohol-induced toxicity [14]. However, the specific underlying mechanisms by which alcohol induces microglial inflammation in the mPFC that contributes to cognitive deficits are still largely elusive.

Mitophagy, a type of conserved specific autophagy, is responsible for maintaining mitochondrial homeostasis by efficiently degrading damaged mitochondria [15]. Two major pathways mediate the process of mitophagy [16,17]. One involves PTEN-induced kinase 1 (PINK1) and parkin RBR E3 ubiquitin protein ligase (PRKN), which accumulate on the mitochondrial membrane and ubiquitinate damaged mitochondria; these proteins are then recognized and targeted for removal by autophagosomes. The other pathway involves receptors on the outer mitochondrial membrane, including BCL2 interacting protein 3 (BNIP3) and BCL2 interacting protein 3 like (BNIP3L/NIX), both of which directly interact with LC3 II on autophagosomes. Conversely, compromised mitophagy in response to cellular stress leads to mitochondrial dysfunction, contributing to neuroinflammation, neurodegeneration and behavioral deficits in diseases of the central nervous system (CNS) [[18], [19], [20], [21]]. However, the roles of mitophagy in alcohol-related cognitive impairment have not yet been well elucidated.

Nuclear factor erythroid 2-related Factor 2 (NRF2) is a transcription factor that plays a pivotal role in cellular defense mechanisms against oxidative stress [22]. The role of NRF2 involves the modulation of mitophagy. Through binding to the PINK1 promoter, NRF2 increases the PINK1 expression, enabling the activation of mitophagy in response to mitochondrial abnormalities [23,24]. In addition, NRF2 has been reported to act as an upstream signaling molecule of BNIP3 [25,26]. Recent studies have indicated that NRF2 represents a promising therapeutic target for the treatment of neurodegenerative diseases [27]. Dysregulation of NRF2 under alcohol exposure conditions has been indicated in previous studies, and enhancing NRF2 signaling attenuates alcohol-induced ROS production and inflammation [[28], [29], [30]]. Therefore, NRF2 activators may be potentially effective treatments for alcohol-related cognitive impairment, and the interaction of NRF2 with mitophagy in the context of alcohol requires further exploration.

In the present study, we explored the role of mitophagy in microglial NLRP3 inflammasome activation under alcohol exposure conditions. Additionally, we investigated whether NRF2 activation by RTA-408 could alleviate alcohol-induced cognitive impairment and microglial NLRP3 inflammasome activation by modulating mitophagy.