Chemokines CXCL9 and CCL2 in Relation to Cerebral White Matter Disease, Cognitive Decline, and Dementia

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Background and Objectives: Chemokines C-X-C Motif Chemokine Ligand 9 (CXCL9) and C-C Motif Chemokine Ligand 2 (CCL2) were previously linked to incident cognitive impairment and dementia in the Northern Manhattan Study (NOMAS). We investigated whether circulating CXCL9 and CCL2 are independently associated with the cerebral white matter disease (WMD) burden and whether WMD mediates their association with prospective cognitive outcomes. Methods: In the stroke-free, prospective, community-dwelling NOMAS cohort (age≥50) we examined white matter hyperintensity volume (WMHV) on brain MRI and serum chemokine levels. WMHV was normalized, log-transformed, and standardized. Cognitive status was assessed at MRI and again 12.2±1.3 years later to adjudicate incident cognitive decline and dementia. Multivariable linear regression models with either CXCL9 or CCL2 (in quartiles) as exposures and WMHV as the outcome were adjusted for socio-demographics and key contributors to WMD, including vascular risk factors (Model 1), kidney function (2), and APOE ε4 status (3). Mediation of the CXCL9-cognitive outcome association by WMHV was tested using Monte Carlo integration. Results: Among 1,179 participants (mean age 70±9 years; 60% female), elevated CXCL9 (Q4 vs. Q1) was associated with greater WMHV (Model 1: β=0.20, 95%CI 0.06-0.34). This association persisted even after adjusting for kidney function (Model 2: β=0.17, 95%CI 0.03-0.34) and APOE ε4 status (Model 3: β=0.19, 95%CI 0.04-0.33). CXCL9 (Q4 vs. Q1) effect magnitude in Model 3 approximated ~4 years of aging (β=0.05/year, 95%CI 0.04-0.06), exceeding that of hypertension (β=0.16, 95%CI 0.05-0.27), with a stepwise trend present across quartiles (β/quartile increase=0.07, 95%CI 0.02-0.12, p=0.003). Among 1,166 participants (dementia-free at MRI), the indirect, WMHV-mediated pathway was statistically significant for the association of CXCL9 with incident cognitive decline (ACME 0.009, 95%CI 0.002-0.018, p=0.016) and with dementia (ACME 0.008, 95%CI 0.003-0.016, p=0.004). CCL2 showed no association with WMHV. Discussion: Greater CXCL9 levels were associated with greater white matter lesion load, independent of vascular, renal, and genetic factors, suggesting a role in WMD pathogenesis. WMHV mediated CXCL9's association with cognitive decline and dementia risk. This IFN-γ-induced monokine (MIG) warrants further evaluation as a biomarker of white matter and cognitive health as well as a potentially modifiable therapeutic target.

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