Figure 7.

RARβ activity regulates H₂O₂ induced cell death. Motor neuron cultures were pre-treated for 1.0 hour with agents that specifically target RARβ prior to the addition of toxin. A: In the presence of adapalene, a RARβ agonist, the percentage of cell death induced by H₂O₂ was significantly reduced when compared to the control treatment of DMSO plus H₂O₂ (compare blue and green curves). Controls of DMSO alone or adapalene alone measured baseline level of cell death over time (black and orange curves). B: Pre-treatment of cells with a combination of ATRA and LE-135, a selective RARβ antagonist, eliminated the protective effects of ATRA and exacerbated the toxicity in the presence or absence of H₂O₂ (green and orange curves). Control treatments of DMSO alone (black curve) or DMSO plus H₂O₂ (blue curve) are shown. Error bars represent the mean percentage of cell death ± standard error of the mean from at least two separate experiments. *p < 0.05; ***p < 0.001.