Maneb-induced oxidative stress drives alpha-synuclein upregulation and glial resolution responses

Abstract

Maneb (MB) is a dithiocarbamate pesticide whose prolonged use is considered an environmental risk factor for Parkinson’s disease (PD). Previous studies from our group and others have demonstrated that MB induces the upregulation of α-synuclein. The pathogenesis of PD is not only linked to α-synuclein accumulation but also to neuroinflammation. Chronic neuroinflammation likely arises from impaired resolution mechanisms that fail to limit early pro-inflammatory responses, ultimately leading to neuronal death. Although resolution pathways in the central nervous system remain poorly characterized, glial cells are considered key candidates to mediate these processes. In this study, we aimed to describe the biochemical events associated with pesticide- induced toxicity, α-synuclein upregulation, neuroinflammation, and neuron–glia crosstalk. For this purpose, we used the astrocytic C6 cell line, primary glial cultures, and dopaminergic neuronal cell lines (IMR-32 and N27) exposed to MB. Their secretomes were collected and used as conditioned media to investigate the biochemical mechanisms underlying resolution responses between neurons and glia. In dopaminergic neurons, α-synuclein upregulation was accompanied by increased reactive oxygen species (ROS), lipid peroxidation, and mitochondrial alterations consistent with ferroptosis. Treatment with the antioxidant N-acetylcysteine and the ferroptosis inhibitor ferrostatin-1 reversed both α-synuclein overexpression and MB-induced mitochondrial disruption. MB exposure also triggered pro-inflammatory signaling, including cyclooxygenase-2 upregulation and nuclear translocation of NF-κB, alongside a reduction in ALOX15 mRNA expression. In astrocytes, MB treatment increased glial fibrillary acidic protein (GFAP) expression. Despite the pro-inflammatory environment, astrocyte viability was only mildly affected, and their secretome was capable of protecting neurons from MB-induced cell death. Furthermore, the secretome from MB-exposed neurons upregulated ALOX15 expression and promoted a proliferative, A2 anti-inflammatory phenotype in astrocytes. In this context, we further explored the role of the pro-resolving lipid mediator lipoxin A4 as a key component of neuron–astrocyte resolution signaling, acting via the G-protein–coupled receptor FPR2/ALX. Our results suggest that, in the context of pesticide-induced neurotoxicity, α-synuclein upregulation is driven by oxidative stress, associated with ferroptosis, and linked to both pro- and anti-inflammatory signaling during the early stages of neurodegeneration