Selective PET Imaging of Astrocytes and Microglia in Alzheimer's Disease

Healthy Clinical Trial

Official title: Selective PET Imaging of Astrocytes and Microglia in Alzheimer's Disease

Status Recruiting

Clinical Trial Summary

Inflammation occurs in many brain diseases including Alzheimer's disease. In Alzheimer's disease, amyloid starts accumulating decades before the start of forgetfulness. Basic scientists have reported that inflammation but not amyloid is linked to forgetfulness. When people pinch a finger, it gets swollen. Similar changes occur in brain from various causes. New medications are under development to help healing and prevent permanent damages in the brain. When people pinch a finger, they can check if the injury is healing or getting worse by watching. Investigators can watch inside of the brain using a special camera called positron emission tomography (PET). It is currently possible to watch inflammation in the brain by taking pictures of a molecule called translocator protein (TSPO). But the problem is that by imaging TSPO, investigators can catch changes in more than one kind of cells. The information is not specific to each cell type. Such vague information is not useful to monitor the effect of new medications for inflammation. This proposal attempts to develop a novel method to capture changes in each of two major players in inflammation, microglia and astrocytes. To do so, investigators will take selective pictures of one cell type by using a novel imaging agent for PET. Investigators will also take PET pictures of TSPO. Investigators will process these two kinds of PET pictures using advanced mathematical methods and extract specific information on microglia and astrocytes. Our novel method will be useful to monitor new therapies to treat inflammation in brain.

Clinical Trial Description

Inflammation in brain plays critical roles in disease progress and symptom development in a number of brain disorders such as Alzheimer's disease (AD), traumatic brain injury, major depressive disorder, epilepsy, and schizophrenia. Neuroinflammation has been imaged using positron emission tomography (PET) by using translocator protein (TSPO) as the marker. Although TSPO PET studies have provided insight to understand the pathology, some results are difficult to interpret. TSPO imaging has a major limitation of not being selective to one type of glia; it is expressed by both microglia and astrocyte. The current study attempts to overcome this limitation. Monoamine oxidase type-B (MAO-B) is highly expressed by astrocyte and serotonin (5-HT)-releasing neurons but not by microglia. PET studies using a prototype tracer 11C-L-deprenyl detects astrogliosis in mild cognitive impairment (MCI) but this tracer has low levels of specific binding. Preliminary results show that a novel tracer 18F-SMBT-1 developed by Dr. Okamura and his colleagues has several times greater levels of specific binding. The Aims of the current study are to 1) estimate radiation-absorbed doses in 8 healthy people, 2) measure ratios of specific-to-nondisplaceable binding by performing brain scans with and without binding blockade in 5 patients with Alzheimer's disease, 3) measure reproducibility of measuring 18F-SMBT-1 in 8 healthy people, 4) compare MAO-B levels between healthy controls (n = 25) and patients with AD (n = 25), and 5) from 11C-ER176 for TSPO and 18F-SMBT-1, extract cell type specific information for microglia and astrocytes and investigate changes in each cell type In AD. ;

Related Conditions & MeSH terms

• Alzheimer Disease
• Healthy

• NCT number: NCT05582200
• Study type: Observational
• Source: The Methodist Hospital Research Institute
• Contact: Masahiro Fujita
• Phone: 7134410803
• Email: mfujita@houstonmethodist.org
• Status: Recruiting
• Start date: January 20, 2023
• Completion date: October 31, 2025