Chronic Paraquat Neurotoxicity and Dopaminergic Degeneration: A Mechanistic Review

Parkinson's disease (PD) is a significant neurodegenerative disorder that affects 1%-2% of the entire global population. Despite its higher prevalence, an effective treatment that prevents or reverses neuronal damage is still not available. Clinical characteristics of PD include bradykinesia, postural instability, tremor, and rigidity. This disease is pathologically defined by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and by Lewy pathology with aggregated α-synuclein (oligomers), although the exact role of Lewy bodies (LB) in cell death is controversial. Like other neurodegenerative disorders, the etiology of PD is associated with genetic, environmental, and other unknown factors. Certain neurotoxins such as rotenone, maneb, 6-OHDA, MPTP and paraquat are main factors in the causation of PD. Among them, paraquat (PQ) is strongly linked with PD because of its common use in developing countries. Many in vitro and in vivo studies have reported the occurrence of PD due to exposure to PQ. The apoptotic cell death caused by PQ is associated with oxidative stress, ER stress, catabolic changes in dopamine, mitochondrial dysfunction, and so forth. The current review will summarize the available scientific evidence concerning the use and impacts of chronic exposure to PQ in the light of PD.