Immunohistochemical expression of IGF‐I and GSK in the spinal cord of Kii and Guamanian ALS patients

Insulin‐like growth factor‐I (IGF‐I) is a potent survival factor for motor neurons in animals, and glycogen synthase kinase‐3β (GSK‐3β) is suspected to play roles in apoptosis and tau phosphorylation. Here we report the immunological expression of IGF‐I, GSK‐3β, phosphorylated‐GSK‐3α/β (p‐GSK‐3α/β) and phosphorylated‐tau in the spinal cord and hippocampus of Kii and Guam amyotrophic lateral sclerosis (ALS) patients. Sixteen ALS patients (10 Japanese sporadic, 3 Kii and 3 Guam ALS) and 14 neurological controls (10 Japanese and 4 Guamanian) were examined. The immunoreactivity for each antibody was rated by the percentages of positive neurons to total anterior horn neurons in each patient and was analyzed statistically. Many normal‐looking neurons from Japanese sporadic ALS, Kii ALS and Guam ALS patients, as well as from Japanese and Guam controls, were positive for anti‐IGF‐I antibody. A positive correlation between IR scores for anti‐IGF‐I antibody and clinical durations of Japanese sporadic ALS patients was found in this study (P < 0.0001). This suggested that IGF‐I might have a protective effect against ALS degeneration. In Japanese sporadic ALS patients, abnormal as well as normal‐looking neurons showed significant high IR scores for anti‐GSK‐3β antibody than those of controls. Anterior horn neurons from Guam and Kii ALS patients characteristically showed weak staining for anti‐GSK‐3β antibody but were markedly positive for anti‐pGSK‐3α/β antibody compared to those from both Japanese controls and Japanese sporadic ALS patients, and showed the co‐localization of IGF‐I and p‐GSK‐3α/β. This suggested that the IGF‐I signaling pathway in Guam and Kii ALS patients might function to phosphorylate GSK‐3β to protect neurons from ALS degeneration. Neurofibrillary tangles (NFTs) in the hippocampus and spinal cord from Kii and Guam ALS patients showed the co‐localization of PHF‐tau and p‐GSK‐3α/β by a confocal laser scanning technique. The predominant expression of p‐GSK‐3α/β compared to GSK‐3β in spinal motor neurons and the co‐localization of p‐GSK‐3α/β and PHF‐tau in NFT‐laden neurons in the hippocampus and spinal cord were characteristic findings of Kii and Guam ALS patients.