Berberine reduced interleukin-1<b>β</b> (IL-1β)-induced activation of mixed glia and microglia and protected neurons against microglia-mediated neurotoxicity <i>in vitro</i>.

<p>(<b>A</b>) Treatment with 1, 5, 10 or 50 µM berberine immediately after stretch injury for 1 day did not affect cell viability by 3-[4,5-dimethyl-2-thiazolyl]- 2,5-diphenyl-2-tetrazolium bromide (MTT) assay. (<b>B</b>) In primary mixed glial cultures, co-treatment of 5, 10, or 50 µM berberine with IL-1β for 1 day significantly reduced IL-1β-induced nitric oxide (NO) production. (<b>C</b>) Experimental scheme of neuronal survival in neuroblastoma neuro-2A (N2A) cells in response to IL-1β-treated BV2-conditioned media with or without berberine pretreatment. BV2 microglia were incubated with 1 µg·mL⁻¹ IL-1β in the absence (IL-1β–CM) or presence of 50 µM berberine (IL-1β/BBR–CM) for 48 h. Cell-free supernatant fractions were applied to N2A cells for 24 h to evaluate the changes in cell viability and cleaved caspase-3 (cCP-3)level. (<b>D</b>) In BV2 microglia, co-treatment of 1, 5, 10, or 50 µM berberine with IL-1β for 2 days significantly reduced IL-1β-induced NO production. Values are presented as mean ± SEM of four independent experiments. ^*<i>P</i><0.05, ^**<i>P</i><0.01, and ^***<i>P</i><0.001 vs. the normal control; ^##<i>P</i><0.01 and ^###<i>P</i><0.001 vs. stretch injury or IL-1β stimulation alone as determined by one-way ANOVA. (<b>E</b>) Neuronal cell death increased after exposure to IL-1β-treated conditioned microglial media; the effect was significantly reduced by microglia pretreatment with 50 µM berberine. (<b>F</b>) Western blot analysis showed that berberine significantly reduced the cCP-3 level compared with N2A cells treated with conditioned microglia media alone. Values are presented as mean ± SEM of four independent experiments. <i>P</i><0.001 vs. the normal control; ^#<i>P</i><0.05, ^###<i>P</i><0.001 vs. N2A cells treated with conditioned microglia media alone as determined by one-way ANOVA.