Evaluation of Chitotriosidase and CC-Chemokine Ligand 18 as Biomarkers of Microglia Activation in Amyotrophic Lateral Sclerosis

Background: The development of biomarkers for use in diagnosing, monitoring disease progression and analyzing therapeutic trials response in amyotrophic lateral sclerosis (ALS) is essential.

Objective: The aim of this study was to identify inflammatory factors in plasma or cerebrospinal fluid (CSF) from patients with ALS with particular attention to specific markers of microglia activation as chitotriosidase (ChT) and chemokine (C-C motif) ligand 18 (CCL18) to determine its potential as ALS biomarkers.

Methods: We studied CSF and plasma samples from 32 patients and 42 healthy controls. We assayed the ChT activity by a spectrofluorometric method and protein levels of other inflammatory -biomarkers (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6 and CCL18) by enzyme-linked immunosorbent assay. CHIT1 gene polymorphism in exon 10 (c.1049_1072dup24) encoding inactive ChT enzyme was genotyped in all subjects.

Results: ChT activity and TNF-alpha protein levels were significantly higher in CSF of ALS patients, but we found no correlation with the severity and progression of the disease. Nevertheless, we did not found any differences in CCL18 or IL-6 protein levels between both groups in CSF or plasma. In our sample, only 3% of subjects were homozygous carriers for the CHIT1 exon 10 duplication associated with defective enzyme.

Conclusions: High ChT activity in CSF of patients with ALS may reflect microglia activation and could be a potential biomarker of the disease. We did not find any significant difference regarding CCL-18, another specific marker of microglia activation that is related with M2-like microglia phenotype. Deepening the understanding of the activation state of microglia (M1 and M2) may contribute to the knowledge about the specific role of neuroinflammation in ALS and future therapeutic strategies.