Systematic literature review on Parkinson's disease and Childhood Leukaemia and mode of actions for pesticides

Abstract

This report presents the outcomes of a systematic review (SR) identifying the mechanisms and chemicals involved in the pathogenesis of Parkinson's disease (PD) and childhood leukaemia (CL). This work serves as a basis for defining and mapping the causal linkages between a molecular initiating event (MIE) and a final adverse outcome (AO) that are relevant for the development of a prototype adverse outcome pathway (AOP) for assessing risk factors for PD and CL. Search for literature from 1990 to present was conducted using Web of Science, PubMed and TOXNET, and relevant references were selected using established inclusion/exclusion criteria and ranked using a set of quality control factors. For PD, 7,384 individual references were identified to be relevant for PD pathogenesis and chemicals associated with PD. Dopaminergic neurodegeneration in the substantia nigra leading to locomotor deficits was identified as the AO in PD. Other identified key events in PD pathogenesis include mitochondrial dysfunction, cellular accumulation of alpha-synuclein and oxidative stress. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, rotenone and paraquat are some chemicals identified to be associated with PD pathogenesis. For CL, 1,988 individual references were identified to be relevant for CL pathogenesis and chemicals associated with CL. Chromosomal translocation, genetic damage/mutation and hyperdiploidy are considered as driving forces of CL. Except for infant leukaemia, CL pathogenesis requires a 'two-hit' model with an initiating event occurring in utero followed by a secondary hit potentially occurring after birth. Potential MIEs leading to these driving mechanisms include aberrant DNA topoisomerase II activity and erroneous DNA repair. Epigenetics appears to also play an influential role in CL pathogenesis. Benzene, bioflavonoids and organophosphates are some chemicals identified to be implicated in CL pathogenesis. The challenges of developing AOPs for these two diseases and the data gaps identified from the outcomes of this SR are also elaborated in this report. SUMMARY The aim of this project was to perform a systematic review (SR) to collect relevant publications related to the mechanisms involved in the pathogenesis of Parkinson's disease (PD) and childhood leukaemia