The Toxmatrix: Chemo-Genomic Profiling Identifies Interactions That Reveal Mechanisms of Toxicity

A chemical
genomics “Toxmatrix” method was developed
to elucidate mechanisms of cytotoxicity using neuronal models. Quantitative
high-throughput screening (qHTS) was applied to systematically screen
each toxicant against a panel of 70 modulators, drugs or chemicals
that act on a known target, to identify interactions that either protect
or sensitize cells to each toxicant. Thirty-two toxicants were tested
at 10 concentrations for cytotoxicity to SH-SY5Y human neuroblastoma
cells, with results fitted to the Hill equation to determine an IC50 for each toxicant. Thirty-three toxicant:modulator interactions
were identified in SH-SY5Y cells for 14 toxicants, as modulators that
shifted toxicant IC50 values lower or higher. The target
of each modulator that sensitizes cells or protects cells from a toxicant
suggests a mode of toxicant action or cellular adaptation. In secondary
screening, we tested modulator-toxicant pairs identified from the
SH-SY5Y primary screening for interactions in three differentiated
neuronal human cell lines: dSH-SY5Y, conditionally immortalized dopaminergic
neurons (LUHMES), and neural stem cells. Twenty toxicant-modulator
pairs showed pronounced interactions in one or several differentiated
cell models. Additional testing confirmed that several modulators
acted through their primary targets. For example, several chelators
protected differentiated LUHMES neurons from four toxicants by chelation
of divalent cations and buthionine sulphoximine sensitized cells to
6-hydroxydopamine and 4-(methylamino)­phenol hemisulfate by blocking
glutathione synthesis. Such modulators that interact with multiple
neurotoxicants suggest these may be vulnerable toxicity pathways in
neurons. Thus, the Toxmatrix method is a systematic high-throughput
approach that can identify mechanisms of toxicity and cellular adaptation.