Depression as a risk factor for Alzheimer's disease: A human post-mortem study

Area of Science:

• Neuroscience
• Psychiatry
• Immunology

Background:

• Depression is a risk factor for Alzheimer's disease (AD), potentially an early AD manifestation.
• Neuroinflammation is a common feature in both depression and AD, but mechanisms linking them are unclear.

Purpose of the Study:

• To investigate neuroinflammation in post-mortem human brain tissue from individuals with depression and early-stage AD.
• To compare inflammatory protein and endothelial marker levels between depressed individuals, AD patients, and controls.

Main Methods:

• Analysis of post-mortem dorsal prefrontal cortex tissue from 54 depressed cases, 37 controls, 16 early-stage AD cases, and 15 controls.
• Measurement of 10 inflammatory proteins (cytokines) and 2 endothelial markers using ELISA and MesoScale Multiplex Assays.

Main Results:

• Depression group showed increased Interleukin-6 (IL-6) and Interleukin-10 (IL-10), and decreased Interleukin-1β (IL-1β) compared to controls.
• Early-stage AD cases exhibited increased ICAM-1, indicating endothelial activation, but no significant changes in measured cytokines.
• Neuroinflammation was evident in depression but not in early-stage AD.

Conclusions:

• Depression is associated with neuroinflammation, while early AD shows endothelial activation without significant cytokine alterations.
• The findings suggest depression may elevate AD risk through mechanisms other than the measured inflammatory pathways.