Metallothionein III Decreases the Proliferation of Astrocytes and Enhances Pathological Improvements in a Mouse Model of Alzheimer's Disease.

Abstract

Alzheimer's disease (AD) affects the brain and causes difficulties with cognition and emotions. At present, there are no viable therapies to halt or slow down the advancement of AD. Metallothionein III (MT-III) exhibits antioxidant and anti-inflammatory characteristics, indicating possible therapeutic benefits. This study aimed to explore the influence of MT-III on AD pathological alterations and cognitive abilities. In this research, we employed the universally accepted AD mouse models (3xTg-AD) as test subjects and administrated vehicle or MT-III. The mice were subjected to the Morris water maze test to assess their spatial learning and memory capabilities. Moreover, to evaluate the consequent effects on neuronal groups in the hippocampus, the Nissl staining and neuronal nuclear antigen (NeuN) immunohistochemistry were used to identify the cellular morphology changes and density. Immunohistochemistry was also used to detect β-amyloid (Aβ) and glial fibrillary acidic protein (GFAP) to measure Aβ accumulation and astrocyte growth. Western blot was also used to measure Tau pathology-related PHD finger protein 1 (PHF-1), phosphorylated Tau (AT-8), and total Tau protein. The administration of MT-III notably enhanced spatial learning and memory function in 3xTg-AD mice, as evidenced by the Morris water maze test (p < 0.01). According to immunohistochemistry and the obtained findings, it was observed that brain tissues of mice treated with MT-III showed a notable increase of Nissl bodies and NeuN intensity (p < 0.01) while a remarkable decrease in Aβ accumulation and GFAP (p < 0.01). Additionally, MT-III largely decreased levels of Tau phosphorylation-related PHF-1 and AT-8 (p < 0.01) and slightly reduced the level of Tau 5 (p < 0.05). In summary, our research indicates that MT-III has the capacity to ameliorate pathological alterations in AD mouse models and safeguard their cognitive and emotional abilities. By decreasing β-amyloid accumulation and reducing the intensity of Tau pathology, MT-III protected hippocampal subfield neurons against pathological harm. Furthermore, MT-III reduced inflammation by inhibiting abnormal proliferation of astrocytes. Of utmost importance, MT-III greatly enhanced the cognitive abilities related to spatial learning and memory in mice, suggesting its promising therapeutic properties for AD.