Complement 3 Is a Potential Biomarker for Cerebral Amyloid Angiopathy.

BACKGROUND

Cerebral amyloid angiopathy is a cerebrovascular disease directly implicated in Alzheimer's disease pathogenesis through amyloid-β deposition. Growing evidence has shown a pivotal role of chronic neuroinflammation both in cerebral amyloid angiopathy and Alzheimer's disease.

OBJECTIVE

The aim of this study was to investigate whether circulating levels of the complement 3, a crucial component of the innate immune system, are increased in patients with cerebral amyloid angiopathy.

METHODS

Serum complement 3 levels were retrospectively measured by a sandwich enzyme-linked immunosorbent assay in a single-center cohort of patients with mild cognitive impairment. The diagnosis of cerebral amyloid angiopathy was based on the modified Boston criteria. Logistic regression analysis was performed to identify the predictive factors for cerebral amyloid angiopathy.

RESULTS

We analyzed 55 mild cognitive impairment patients (mean age [standard deviation]: 76.3 [6.8] years; 33 [60% ] men). Complement 3 levels were significantly increased in cerebral amyloid angiopathy patients (n = 16) compared with those without cerebral amyloid angiopathy (n = 39) (median [interquartile range]: 0.43 [0.34-0.65] versus 0.35 [0.25-0.45], respectively; p = 0.040). Univariate and multivariate logistic regression analysis revealed that increased complement 3 levels were significantly associated with cerebral amyloid angiopathy. After selection of the best predictive model using stepwise selection, complement 3 was preserved as a significant independent predictive factor for cerebral amyloid angiopathy (odds ratio per 0.1 unit/mL increase [95% confidence interval]: 1.407 [1.042-1.899]; p = 0.026).

CONCLUSION

Complement activation may play a pivotal role in cerebral amyloid angiopathy. Complement 3 may be a novel diagnostic biomarker for cerebral amyloid angiopathy.