Figure 8

Protective effect of exogenous TNF-α or IL-6 against METH-induced microglial cell death. (A) TNF-α (1 ng/mL) completely prevented the increase of TUNEL-positive cells induced by METH; this was abolished by IL-6R antibody (10 μg/mL). (B) IL-6 (1 ng/mL) reduced the number of TUNEL-positive cells, and once again the blockade of its receptor with IL-6R antibody abolished this effect. Also, the JAK-STAT3 inhibitor (20 μM AG 490) exacerbated METH toxicity. The results are expressed as mean percentage of total cells ± SEM (n = 17 to 41). ^*** P <0.001, Dunnett’s multiple comparison test, significantly different when compared to control; ⁺⁺ P <0.01, ⁺⁺⁺ P <0.001, Bonferroni’s multiple comparison test, significantly different when compared with 1 mM METH; ^§§§ P <0.001, Bonferroni’s multiple comparison test, significantly different when compared with 1 mM METH plus TNF-α or IL-6. (C) Representative images of pSTAT3 immunoreactivity (red) in N9 microglial cells under control conditions and exposed to 1 mM METH alone or in the presence of 1 ng/mL IL-6. Cells were also stained with Hoechst 33342 (blue). Scale bar, 20 μm and 50 μm. IL-6: interleukin 6; JAK-STAT: janus kinase-signal transducer and activator of transcription; METH: methamphetamine; pSTAT: phospho-signal transducer and activator of transcription; SEM: standard error of the mean; TNF-α: tumor necrosis factor-alpha; TUNEL: terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay.