ABSTRACT
Aim To investigate whether pioglitazone has protective effect against glutamate induced neurotoxicity in cultured cortical neurons and its possible molecular mechanisms underlying pioglitazone's neuroprotective effects.Methods The cortical neurons were taken from newborn rats and used for experiments 7 days after culture.The neurons were randomly divided into control group;glutamate group; glutamate+piogli-tazone group;glutamate+SP600125 group;SP600125 group.Cell viability was determined by MTT.The morphology change of neurons was observed under a fluorescence microscope with fluorescence dye Hoechst 33258.Immunostaining was used to investigate the expression of phospho-ATF2 in neuronal cells.Western blot was performed to investigate the protein level of phospho-JNK1 and total JNK1.Results Pioglitazone markedly reduced the damage of cortical neurons caused by glutamate.Pioglitazone also significantly inhibited glutamate induced up-regulation of phospho-JNK1 protein level and phospho-ATF2 expression.SP600125, an inhibitor of JNK, antagonized the toxicity induced by glutamate.Conclusions Pioglitazone can protect cultured cortical neurons from glutamate induced damage.The protective effect of pioglitazone appears to be associated with inhibiting the c-Jun N-terminal protein kinase signaling pathway.
ABSTRACT
AIM To investigate whether pioglitazone can protect cortical neurons from lipopolysaccharides(LPS)-induced neurotoxicity and the mechanisms responsible for this protective effect. METHODS After 7 d cultures，cultured cortical neurons were incubated with LPS 10 mg·L~(-1) for 4-24 h with or without other drugs. In co-incubation experiments, other drugs were added to the neurons 30 min or 1 h prior to incubation with LPS. The cell viability was assessed by MTT assay. The neuronal apoptosis was quantified by scoring the percentage of cells with apoptotic nuclear morphology after Hoechst 33258 staining. The cultured cells were then fixed on the 7th day and immunocytochemically stained with phosphorylated JNK1 antibody. The protein expressions of active caspase 3 and phosphorylated JNK1 were measured by Western blot. Nitric oxide (NO) generation was measured by Griess method. RESULTS The decrease of cell viability and the increase of apoptotic cells in cultured cortical neurons were observed incubated with LPS for 24 h compared with the normal controls. The cell viability of cortical neurons was decreased from (100.0±10.9)% in the normal control group to (72.3±2.1)% in the LPS-treated group and the apoptotic cell percentages were increased from (11.5±4.2)% in the normal control group to (39.5±8.2)% in the LPS group. LPS induced the increases in phospho-JNK1, active caspase 3 expression, and NO generation. Pioglitazone 0.01, 0.1 and 1 μmol·L~(-1), respectively inhibited LPS-induced decrease in cell viability and increase of apoptotic morphology, active caspase 3 expression in cultured neurons. In LPS+pioglitazone 1 μmol·L~(-1) group, cell viability was （97.8±9.7）%, the apoptotic cells percentage was (20.6±5.0)%, NO generation (6.8±1.3)μmol·L~(-1). Furthermore, pioglitazone also inhibited LPS-induced the increase in JNK1 phosphorylation and NO generation. JNK inhibitor SP600125 5 μmol·L~(-1) significantly inhibited LPS-induced neurotoxicity, cell viability was increased from (72.3±2.1)% to (109.8±11.8)%, the apoptotic cells percentage from (39.5±8.2)% decreased to (19.1±4.8)%, NO generation from （21.1±5.0）μmol·L~(-1) decreased to（4.0±1.3）μmol·L~(-1). The PPARγ antagonist GW9662 10 μmol·L~(-1) did not reverse the effects of pioglitazone. In LPS+pioglitazone 1 μmol·L~(-1)+GW9662 10 μmol·L~(-1) group, cell viability was (90.7±6.9)%, the apoptotic cells percentage was (23.4±4.1)%, and NO concentration was (5.8±0.7)μmol·L~(-1). CONCLUSION Pioglitazone protects cortical neurons against LPS insult at least via inhibiting JNK activity and NO generation, but not PPARγ activation.