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Insulin-like growth factor-I (IGF-I) is a potent survival factor for motor neurons in animals, and glycogen synthase kinase-3beta (GSK-3beta) is suspected to play roles in apoptosis and tau phosphorylation. Here we report the immunological expression of IGF-I, GSK-3beta, phosphorylated-GSK-3alpha/beta (p-GSK-3alpha/beta) 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-3beta antibody than those of controls. Anterior horn neurons from Guam and Kii ALS patients characteristically showed weak staining for anti-GSK-3beta antibody but were markedly positive for anti-pGSK-3alpha/beta antibody compared to those from both Japanese controls and Japanese sporadic ALS patients, and showed the co-localization of IGF-I and p-GSK-3alpha/beta. This suggested that the IGF-I signaling pathway in Guam and Kii ALS patients might function to phosphorylate GSK-3beta 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-3alpha/beta by a confocal laser scanning technique. The predominant expression of p-GSK-3alpha/beta compared to GSK-3beta in spinal motor neurons and the co-localization of p-GSK-3alpha/beta and PHF-tau in NFT-laden neurons in the hippocampus and spinal cord were characteristic findings of Kii and Guam ALS patients.

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease involving the upper and lower motor neuron systems. Activated microglia are reported to enhance motor neuron death by secreting neurotoxic cytokines in SOD1-transgenic mice. Recent studies have provided evidence that chronic stimulation leads microglia to acquire an anti-inflammatory phenotype, characterized by activated morphology and induction of neuroprotective and immunoregulatory molecules. However, little information is available on the protective functions of microglia in the ALS spinal cord. To investigate the roles of microglia in ALS, we examined the appearance of ionized calcium-binding adaptor molecule 1-positive (Iba1-positive) microglia as correlated to the disease duration and immunohistochemical expression of neurogrowth factors in the ALS spinal cord. In this study, the number of Ibal-positive rod-like microglia significantly increased in the ALS spinal cord compared to controls. The number of ramified microglia was positively correlated with the number of normal-looking neurons and clinical duration of ALS patients; however, the number of rod-like microglia was not correlated with that of abnormal neurons, nor with the clinical duration of the disease. Some rod-like microglia were positive for anti-insulin-like growth factor-II (IGF II) and anti-leukemia inhibitory factor (LIF) immunostaining. Motor neurons in the ALS spinal cords also showed immunore-activity for IGF-II, LIF and the receptors of IGF-II and LIE Taken together, these findings suggest that at least some microglia might have a protective effect on motor neurons in the ALS spinal cord. Neuroprotective and/or neurotoxic effects of microglia on motor neurons should be further studied.

Parkinsonism-dementia complex (PDC) and amyotrophic lateral sclerosis (ALS) are fatal neurological diseases. The incidence on Guam was very high between 1950 and 1965 but decreased dramatically after 1965. It is thought that drinking water containing low levels of calcium (Ca) and magnesium (Mg), and high levels of aluminum and of a plant excitatory neurotoxin are involved in the pathogenesis of these diseases. The present experiment was performed in rats that were exposed to low Ca and/or Mg intake over two generations, thus simulating the conditions of human life on Guam, where several generations live continuously in the same environment. Significant loss of dopaminergic neurons was identified exclusively in the substantia nigra in 1-year-old rats that had been exposed continuously to low Mg intake (one-fifth of the normal level) over generations. The present study suggests that low Mg intake over generations may be involved in the pathogenesis of substantia nigra degeneration in humans.

We investigated the FKBP12 immunoreactivity in the spinal cord of neurological controls and motor neuron disease (MND) patients. In the neurological controls, the spinal neurons were markedly stained with antihuman FKBP12 (N-19 and C-19) antibodies. FKBP12 immunoreactivity was associated with lipofuscin in formalin-fixed paraffin-embedded samples. In an electron microscopic view, the 10-nm colloidal gold particles labeled by the anti-FKBP12 (N-19) antibody were present on the lipofuscin of the spinal anterior horn neurons. In the MND cases, atrophic neurons with an abundance of lipofuscin granules in the anterior horns of the spinal cord were mildly stained with the anti-FKBP12 (N-19 and C-19) antibodies. Normal-appearing neurons, inclusion-laden neurons and chromatolytic neurons of MND cases were weak or negatively stained with anti-FKBP12 (N-19) antibodies. These findings suggest that FKBP12 (N-19) may decrease in the early stages of degeneration in MND. Complexes of FKBP12 and ligands were reported to have neuroprotective and/or neuroregenerative properties. It is speculated that the decrease in FKBP12 (N-19) plays some causative role in the development of neurodegeneration in MND. Further investigation of FKBP12 and ligands may help elucidate the pathogenesis of MND.

To evaluate the causative role of environmental aluminum (Al) in the development of neurodegeneration in Kiiamyotrophic lateral sclerosis (ALS), we examined how chronic exposure to a low-Ca/Mg and high-Al diet induced neuronal loss and tau-related neuronal degeneration in experimental animals. Optical microscopic examination showed tau-positive cells, atrophic neurons with darkly stained cytoplasms or swollen perikarya in the cerebrum, hippocampus and the brainstem of mice fed a low-Ca/Mg high-Al diet (Group 3). The neuronal loss was found in the frontal and parietal cortices of the mice and was not due to a classical apoptosis as detected by the terminal de ynucl otidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL) method. Neuronal degeneration and spheroid formation was also seen in the spinal cord of the Group 3 mice. The Morin fluorescence technique showed Al and Ca deposition in the cortical neurons and vessels in the basal ganglia of these mice. An electron microscopic examination showed intranuclear filamentous structures, intracytoplasmic vacuoles and/or darkly stained cytoplasm in the cortical neurons of Group 3 mice. These findings were seen in mice of the 11-month-experimental period and increased until the 25-month-experimental period. The present findings suggested that chronic exposure to a low-Ca/Mg high Al condition induced an accumulation of hyperphosphorylated tau in the cortical neurons, swelling of the neuronal cytoplasm and loss in the cerebrum and spinal cord of mice. Environmental factors such as a low-Ca/Mg high Al exposure might be one of the risk factors for the development of neuronal degeneration of ALS in the Kii Peninsula.