Mitochondrial toxins inhibit the IL-4-induced decrease in LPS-stimulated IL-6 and TNF-α release. Microglial cells were treated with rotenone or 3-NP and stimulated with 10 ng/ml IL-4. After 24 hrs, 1 μg/ml LPS was added for 18 hrs. IL-6 (a, d), TNF-α (b, e) and IL-1β (c, f) were measured as described in Methods. Values are mean ± SEM for independent cytokine measurements. n = 6-16 wells (i.e., 3-8 separate experiments performed in duplicate); *= p < 0.05, **= p < 0.001, ***= p < 0.001, significantly different from corresponding basal (ANOVA followed by Bonferroni's Multiple Comparison test).