Apocynin Prevents Cigarette Smoke-Induced Anxiety-Like Behavior and Preserves Microglial Profiles in Male Mice

Abstract

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death globally and is primarily caused by cigarette smoking (CS). Neurocognitive comorbidities such as anxiety and cognitive impairments are common among people with COPD. CS-induced lung inflammation and oxidative stress may “spill-over” into the systemic circulation, driving the onset of these comorbidities. We investigated whether a prophylactic treatment with the NADPH Oxidase 2 (NOX2) inhibitor, apocynin, could prevent CS-induced neurocognitive impairments. Adult male BALB/c mice were exposed to CS (9 cigarettes/day, 5 days/week) or room air (sham) for 8 weeks with co-administration of apocynin (5 mg/kg, intraperitoneal injection once daily) or vehicle (0.01% DMSO in saline). Following 7 weeks of CS exposure, mice underwent behavioral testing to assess recognition and spatial memory (novel object recognition and Y maze, respectively) and anxiety-like behaviors (open field and elevated plus maze). Mice were then euthanized, and blood, lungs, and brains were collected. Apocynin partially improved CS-induced lung neutrophilia and reversed systemic inflammation (C-reactive protein) and oxidative stress (malondialdehyde). Apocynin exerted an anxiolytic effect in CS-exposed mice, which was associated with restored microglial profiles within the amygdala and hippocampus. Thus, targeting oxidative stress using apocynin can alleviate anxiety-like behaviors and could represent a novel strategy for managing COPD-related anxiety disorders.

Keywords

• cigarette smoking
• lung inflammation
• anxiety
• cognition
• microglia
• neurogenesis