Prepubertal exposure to Pb alters autophagy in the brain of aging mice: A time-series based model

Abstract

As a ubiquitous toxic heavy metal, lead (Pb) exposure is known to be implicated in the onset and development of neurodegenerative diseases which may cause more serious health hazards with age and the accumulation of Pb in the body. Autophagy is the main degradation route for abnormal aggregated proteins and damaged cell organelles. Here, we aimed to study the effects of adolescent Pb exposure on autophagy at different life nodes. In this study, we developed a time-series model of Pb exposure in mice and randomly divided 4-week-old male C57BL/6 mice into six groups (4 C, 13 C, 16 C, 4Pb, 13Pb and 16Pb). Mice in Pb groups was consumed deionized water containing 0.2 % Pb(Ac)2 for 3 months and then reared to anticipated life nodes, while the control group consumed deionized water. Western blot and Real-time qPCR were used to assess the effects of developmental Pb exposure on individual components of the autophagy machinery and modulation of microtubule-associated protein 1 light chain 3 (LC3) at each age stage. Our results showed that Pb exposure during adolescence reduced the p-mTOR/mTOR ratios with enhanced expression of Beclin-1, Atg12 and Atg7in both the hippocampus (HPC) and prefrontal cortex (PFC) of senescent mice while upregulation of LC3II/LC3I ratios and p62 suggested that autophagy mediates degradation was interrupted. Overall, we confirm that Pb exposure during adolescence promotes autophagic processes in the aged mice brain and that autophagic degradation is hindered, ultimately leading to a failure of autophagic degradation.