Activation of STAT3 and inhibitory effects of pioglitazone on STAT3 activity in a mouse model of SOD1-mutated amyotrophic lateral sclerosis

Abstract

Signal transducer and activator of transcription-3 (STAT3) is a member of the proinflammatory transcription factor STAT family. Several studies have documented implications for neuroinflammation in amyotrophic lateral sclerosis (ALS). We recently demonstrated activation of STAT3 in spinal cords obtained at autopsy from sporadic ALS patients. To determine the involvement of STAT3 and effects of pioglitazone on STAT3 activity in familial ALS with superoxide dismutase-1 (SOD1) mutation, we performed immunoblot and immunohistochemical analyses of the active form of STAT3 (p-STAT3) in spinal cords from mice overexpressing mutant SOD1 (ALS mice) and nontransgenic littermates (control mice). Immunoblot analysis delineated significant increases in nuclear p-STAT3 levels in non-treated ALS mice as compared with pioglitazone-treated ALS mice and non-treated and pioglitazone-treated control mice. Immunohistochemical analysis revealed prominent p-STAT3 accumulations in the nucleus of motor neurons, reactive astrocytes and activated microglia in non-treated ALS mice but not pioglitazone-treated ALS mice and non-treated and pioglitazone-treated control mice. The present results provide in vivo evidence for increased phosphorylative activation and nuclear translocation of STAT3 in motor neurons and glia in mouse motor neuron disease, suggesting a common pathological process between sporadic and SOD1-mutated familial forms of ALS. Moreover, it is likely that pioglitazone may exert inhibitory effects on STAT3-mediated proinflammtory mechanisms in this disease.