Lead as a toxic environmental toxicant in models of synucleinopathies

AbstractLead, a toxic heavy metal, is prevalent in various industrial applications, contributing to environmental contamination and significant health concerns. Lead affects various body systems, especially the brain, causing long-lasting cognitive and behavioral changes. While most studies have focused on continuous lead exposure, intermittent exposure, such as that caused by migration or relocations, has received less attention. Importantly, lead exposure intensifies the severity of Parkinson’s disease (PD) and dementia with Lewy bodies, diseases involving the accumulation of alpha-synuclein (aSyn) in the brain and in the gut. Although, the precise mechanisms underlying these observations remain unclear, oxidative stress and mitochondrial dysfunction likely play a role. Here, we investigated how two different profiles of lead exposure - continuous and intermittent - affect models of synucleinopathies. We found that lead exposure enhances the formation of aSyn inclusions, resulting in an increase in both their number and size in cell models. In addition, we found that animals injected with aSyn pre-formed fibrils display serine 129-phosphorylated aSyn inclusions and a reduction in astrocytes in the substantia nigra. These animals also display neuronal damage and alterations in locomotor activity, exploratory behavior, anxiety, memory impairments and hypertension. Our results suggest a mechanistic link between environmental lead exposure and the onset and progression of diseases associated with aSyn pathology. Understanding the molecular and cellular interactions between lead and aSyn is crucial for shaping public health policies and may provide novel insight into strategies for mitigating the impact of environmental toxins on neurodegenerative processes involved in Parkinson’s disease and related synucleinopathies.Key points summaryLead exposure increases the number and size of alpha-synuclein (aSyn) inclusions in cell models.∼Animals exposed to aSyn fibrils and lead show increased phosphorylation of aSyn, neuronal damage and reduced astrogliosis in thesubstantia nigra.Lead-exposed animals exhibit impaired locomotion, anxiety, memory deficits, hypertension and chemoreceptor reflex hypersensitivity.The study suggests a mechanistic link between environmental lead exposure and the progression of diseases involving aSyn pathology, such as Parkinson’s disease.