Cytokines and immune biomarkers in neurodegeneration and cognitive function: A systematic review among individuals of African ancestry

Abstract

BACKGROUND: Cytokines and immune markers are critical in mediating inflammation associated with neurodegenerative disease. This review analyzes the role of inflammatory cytokines and immune markers in neurodegeneration among African populations. METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted a systematic review of studies examining cytokine levels in neurodegenerative diseases, focusing on populations of African ancestry. RESULTS: Cytokines like interleukin (IL)-6, soluble tumor necrosis factor receptor 1, plasma brain-derived neurotrophic factor, and IL-8. IL-6 emerged as a key pro-inflammatory marker linked to neurodegenerative diseases and cognitive decline, showing stronger correlations in African ancestry populations compared to Caucasians. Genetic findings revealed triggering receptor expressed on myeloid cells 2 variants and Fc fragment of IgG receptor IIb rs1050501 genotypes as influential in Alzheimer's disease (AD)-related inflammation, alongside a unique correlation between immunoglobulin G index inflammatory markers and AD in African ancestry populations. DISCUSSION: The findings emphasize the crucial role of cytokines in the pathophysiology of neurodegenerative diseases. Understanding their variations among African populations can inform targeted therapeutic strategies and improve patient outcomes. Highlights: Interleukin (IL)-6 was identified as a key pro-inflammatory marker, consistently linked to Alzheimer's disease (AD), Parkinson's disease, and dementia, underscoring its significant role in neurodegenerative disease progression. Brain-derived neurotrophic factor levels were associated with improved cognitive performance, particularly in African American participants. Observational studies identified sex-based differences in IL-10 levels, particularly among older African American women. The review highlights notable ethnic differences in cytokines like IL-8, IL-1β, and soluble tumor necrosis factor receptors, emphasizing their roles in neurodegeneration and cognitive decline in people of African descent. Triggering receptor expressed on myeloid cells 2 variants, immunoglobulin GM allotypes, and Fc fragment of IgG receptor IIb rs1050501 genotypes were found to influence AD-related inflammation and progression in African ancestry populations.