Effects of chronic low dose rotenone treatment on human microglial cells

Abstract

BackgroundExposure to toxins/chemicals is considered to be a significant risk factor in the pathogenesis of Parkinson's disease (PD); one putative chemical is the naturally occurring herbicide rotenone that is now used widely in establishing PD models. We, and others, have shown that chronic low dose rotenone treatment induces excessive accumulation of Reactive Oxygen Species (ROS), inclusion body formation and apoptosis in dopaminergic neurons of animal and human origin. Some studies have also suggested that microglia enhance the rotenone induced neurotoxicity. While the effects of rotenone on neurons are well established, there is little or no information available on the effect of rotenone on microglial cells, and especially cells of human origin. The aim of the present study was to investigate the effects of chronic low dose rotenone treatment on human microglial CHME-5 cells.MethodsWe have shown previously that rotenone induced inclusion body formation in human dopaminergic SH-SY5Y cells and therefore used these cells as a control for inclusion body formation in this study. SH-SY5Y and CHME-5 cells were treated with 5 nM rotenone for four weeks. At the end of week 4, both cell types were analysed for the presence of inclusion bodies, superoxide dismutases and cell activation (only in CHME-5 cells) using Haematoxylin and Eosin staining, immunocytochemical and western blotting methods. Levels of active caspases and ROS (both extra and intra cellular) were measured using biochemical methods.ConclusionThe results suggest that chronic low dose rotenone treatment activates human microglia (cell line) in a manner similar to microglia of animal origin as shown by others. However human microglia release excessive amounts of ROS extracellularly, do not show excessive amounts of intracellular ROS and active caspases and most importantly do not show any protein aggregation or inclusion body formation. Human microglia appear to be resistant to rotenone (chronic, low dose) induced damage.

Mitochondrial dysfunction in glial cells: Implications for neuronal homeostasis and survival

“…The M1 phenotype of microglia was recently reported to be paralleled by a metabolic switch from mitochondrial OXPHOS to glycolysis that enhances carbon flux to the PPP (Figure 1.5) (Gimeno-Bayon et al 2014; Orihuela et al 2016; Voloboueva et al 2013). Interestingly, inhibition of complex I activity activates microglial cells (Shaikh and Nicholson 2009; Ye et al 2016; Yuan et al 2013), while impairment of mitochondrial fission reduces the production of pro-inflammatory signals (Park et al 2013). Induction of the M2-like phenotype results in no observable changes in mitochondrial oxygen consumption or lactate production (Orihuela et al 2016).…”

Delayed activation of human microglial cells by high dose ionizing radiation

“…To address this question we analyzed the cells for modulation of Glut-5 and CR3/ 43, two human microglial activation markers, by Western blot (Graeber et al, 1994;Shaikh and Nicholson, 2009). The morphology of the cells was examined daily.…”

Molecular mechanisms of pesticide-induced neurotoxicity: Relevance to Parkinson's disease

“…Recent reports demonstrated that ROS induced by rotenone are involved in dopamine redistribution to the cytosol, whose pro-oxidant conditions might potentiate rotenone-induced apoptosis of dopaminergic cells [182, 194, 195]. Similar to paraquat, rotenone activates microglial cells which might act as an important source for ROS [196]. Although rotenone has represented a useful experimental model of neurotoxicity, it lacks significant specificity for the central nervous system.…”