Decreased interleukin-8 levels in the peripheral blood of Alzheimer's patients

IntroductionMultiple studies have reported variations in inflammatory levels in blood of Alzheimers disease (AD), although further research is needed to identify discriminatory biomarkers for AD diagnosis. MethodsA prospective comparative paired study of a group of AD patients compared to normal controls (NC) was carried out in a multicenter study, where age and sex ratio were homogenized to avoid bias. The cohort comprised 39 patients with a diagnosis of AD (64.1% women; mean age 74.8{+/-}0.8 years) and 27 matched NC (66.7% women; 74.8{+/-}0.8 years). The diagnosis of AD was performed by neurologists using the Mini-Mental State Examination test (MMSE) and classical markers in cerebrospinal fluid (CSF) and/or amyloid-PET. We investigated the discriminatory potential of 13 serological parameters in blood, consisting of seven interleukins (IL-3, IL-4, IL-5, IL-6, IL-8, IL-12p40, and IL-15) and other 6 serological inflammatory markers (EGF, GM-CSF, IP-10, sCD40L, PDGF-AB/BB, and RANTES). Additionally, six sociodemographic variables were examined. Apolipoprotein E (APOE) genotype was also determined. ResultsThe results revealed an inverse association between educational level, number of languages spoken, and physical activity, with the risk of AD. An enrichment of the APOE4 isoform was observed in AD (28 out of 39 AD vs 3 out of 24 NC). All circulating inflammation markers were lower in AD patients than in NC (except for IP-10 and sCD40L, while Il-3 and GM-CSF were undetectable in both groups), with statistically significant differences detected in IL-8, IL-12p40, and PDGF-AB/BB (AD/NC ratios of 0.56, 0.59, and 0.81, respectively). IL-8 was decreased specifically in APOE4 carriers (carriers/non-carriers ratio of 0.73), and in amyloid-positive cases (positives/NC ratio of 0.46), whereas IL-12p40 and PDGF-AB/BB showed positives/NC ratios of 0.56 and 0.83, respectively. DiscussionSerum levels of IL-8, IL-12p40, and PDGF-AB/BB were significantly reduced in AD patients. Additionally, IL-8 decrease was associated with APOE4-carriers and amyloid-positive cases.