Chronic thrombin exposure results in an increase in apolipoprotein-E levels

Area of Science:

• Neuroscience
• Biochemistry
• Pathology

Background:

• Traumatic brain injury (TBI) and apolipoprotein E4 (ApoE4) allele inheritance are linked to poor neurological outcomes and increased Alzheimer's disease (AD) risk.
• The role of thrombin in TBI-induced ApoE changes and subsequent amyloidogenesis requires further investigation.

Purpose of the Study:

• To investigate if thrombin released during brain injury elevates apolipoprotein E (ApoE) levels.
• To determine if elevated ApoE4 levels contribute to amyloidogenic effects and cognitive deficits.

Main Methods:

• Rats received intracerebroventricular (i.c.v.) infusion of either thrombin or vehicle for 28 days.
• Human ApoE4 was infused i.c.v. into rats for 56 days.
• Apolipoprotein E levels, beta-amyloid deposition, GFAP-positive astrocytes, and spatial memory were assessed.

Main Results:

• Thrombin treatment significantly increased hippocampal ApoE levels compared to vehicle.
• ApoE4 infusion led to beta-amyloid deposition and increased GFAP-positive astrocytes.
• ApoE4 infusion resulted in significant spatial memory deficits.

Conclusions:

• Thrombin released during brain injury may elevate ApoE levels.
• Elevated ApoE4 levels can promote beta-amyloid deposition.
• Increased ApoE4 is associated with cognitive deficits, suggesting a mechanism contributing to AD pathogenesis after TBI.