Neurofilament 200 as an Indicator of Differences Between Mipafox and Paraoxon Sensitivity in SY5Y Neuroblastoma Cells

Abstract

Organophosphorus (OP) compounds produce potent neurotoxic effects in humans, including organophosphorus-induced delayed neuropathy (OPIDN). This investigation examined the potential for the 200-kD neurofilament protein (NF200) and other neuronal proteins to serve as indicators for neurite damage in a differentiated SY5Y human neuroblastoma cell culture system. Mipafox, which induces OPIDN, increased NF200 protein expression in SY5Y cells differentiated with human recombinant β-nerve growth factor (NGF, 20 ng/ml) in a concentration-dependent manner, compared to NGF controls, when SY5Y cells were exposed to 0.3 or 30 μ M mipafox during the last 5 days of neurite extension (experimental set A). However, mipafox produced little change in NF200 protein expression in SY5Y cells exposed continuously throughout neurite elongation (experimental set B). Paraoxon (up to 30 μ M), which does not produce OPIDN, did not produce any change in NF200 expression in set A or set B. The upregulation of NF200 by mipafox may represent a compensatory response to neurite degeneration. Two other neuronal proteins, growth-associated protein 43 (GAP43) and microtubule-associated protein 2ab (MAP2ab), showed no changes in response to OP treatment in NGF-treated cells. Protein expression of NF200 was shown to be an indicator by which the sensitivities of SY5Y cells to mipafox and paraoxon were distinguishable at the molecular level. These results indicate an alternative approach and test system for investigating structure–activity relationships of OPs.