The exposure to the air pollutant fine particulate matter (PM2.5) slightly enhances high-fat diet-induced anxiety-like behavior and impairs brain redox balance in female rats

Introduction: Obesity is a major risk factor for mood disorders. Additionally, the pollutant fine particulate matter (PM 2.5 ) has effects on central nervous system (CNS) that demand elucidation. Objective: To evaluate if PM 2.5 potentiates the neuropsychological and oxidative effects of obesity. Methods: Female Wistar rats received high-fat (HFD) or standard diet ad libitum for 24 weeks and were daily exposed to 250 µg of PM 2.5, or saline (50 µL), via intranasal instillation. In the last two days, animals underwent open field and elevated plus maze tests. Brain structures were collected for oxidative stress evaluation. Results: HFD and PM 2.5 had independent and cumulative effects on anxiety-like behaviors. HFD reduced exploration in the open field, whereas PM 2.5 enhanced the time spent in the closed arms of the elevated plus maze. Additionally, animals exposed to pollution were more susceptible to the effects of diet in reducing rearing frequency, suggesting subtle cumulative effects. Obese rats exposed to PM 2.5 presented higher lipoperoxidation in hippocampus. Conversely, HFD decreased lipoperoxidation and SOD defense in the cortex, while PM 2.5 primarily affected the cerebellum’s antioxidant defense. Conclusion: PM 2.5 and obesity have independent effects, and their association increases vulnerability to each other’s neurobehavioral and oxidative impacts.