Genetic correlational analysis reveals no association between MPP+ and the severity of striatal dopaminergic damage following MPTP treatment in BXD mouse strains

MPTP neurotoxicity is highly concordant between the sexes among BXD recombinant inbred mouse strains

Continuing our previous work in which we showed wide-ranging strain differences in MPTP neurotoxicity in male mice among ten BXD recombinant inbred strains, we replicated our work in females from nine of the same strains. Mice received a single s.c. injection of 12.5mg/kg MPTP or saline. Forty-eight hours later the striatum was dissected for neurochemical analysis. Striatal dopamine (DA) and its metabolites, DOPAC and HVA, striatal serotonin (5-HT) and its metabolite, 5-HIAA, were analyzed using HPLC. Tyrosine hydroxylase (TH) and glial fibrillary acidic protein (GFAP), an astrocytic protein that increases during the astroglial response to neural injury, were measured using ELISA. There were wide genetic variations in the DA, DOPAC, HVA, TH and GFAP responses to MPTP. We also performed principal component analysis (PCA) on the difference values, saline minus MPTP, for DA, DOPAC, HVA and TH and mapped the dominant principal component to a suggestive QTL on chromosome 1 at the same location that we observed previously for males. Moreover, there were significant correlations between the sexes for the effect of MPTP on DA, HVA, and TH. Our findings suggest that the systems genetic approach as utilized here can help researchers understand the role of sex in individual differences. The same approach can pave the way to understand and pinpoint the genetic bases for individual differences in pathology attributable to toxicants. Such systems genetics approach has broad implications for elucidating gene-environment contributions to neurodegenerative diseases.

Neurotoxin mechanisms and processes relevant to Parkinson's disease: an update

The molecular mechanism responsible for degenerative process in the nigrostriatal dopaminergic system in Parkinson's disease (PD) remains unknown. One major advance in this field has been the discovery of several genes associated to familial PD, including alpha synuclein, parkin, LRRK2, etc., thereby providing important insight toward basic research approaches. There is an consensus in neurodegenerative research that mitochon dria dysfunction, protein degradation dysfunction, aggregation of alpha synuclein to neurotoxic oligomers, oxidative and endoplasmic reticulum stress, and neuroinflammation are involved in degeneration of the neuromelanin-containing dopaminergic neurons that are lost in the disease. An update of the mechanisms relating to neurotoxins that are used to produce preclinical models of Parkinson´s disease is presented. 6-Hydroxydopamine, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and rotenone have been the most wisely used neurotoxins to delve into mechanisms involved in the loss of dopaminergic neurons containing neuromelanin. Neurotoxins generated from dopamine oxidation during neuromelanin formation are likewise reviewed, as this pathway replicates neurotoxin-induced cellular oxidative stress, inactivation of key proteins related to mitochondria and protein degradation dysfunction, and formation of neurotoxic aggregates of alpha synuclein. This survey of neurotoxin modeling-highlighting newer technologies and implicating a variety of processes and pathways related to mechanisms attending PD-is focused on research studies from 2012 to 2014.

Toxicogenetics: in search of host susceptibility to environmental toxicants

Heavy metals, various pesticide and herbicides are implicated as risk factors for human health. Paraquat, maneb, and rotenone, carbamate, and organophosphorous insecticides are examples of toxicants for which acute and chronic exposure are associated with multiple neurological disorders including Parkinson’s disease. Nevertheless, the role of pesticide exposure in neurodegenerative diseases is not clear-cut, as there are inconsistencies in both the epidemiological and preclinical research. The aim of this short review is to show that at least, some of the inconsistencies are related to individual differences in susceptibility to the effects of neurotoxicants, individual differences that can be traced to the genetic constitution of the individuals and animals studies, i.e., host-based susceptibility.