Chitotriosidase, a biomarker of Amyotrophic Lateral Sclerosis accentuates neurodegeneration in spinal motor neurons through neuroinflammation.

Abstract

Background: Cerebrospinal fluid from Amyotrophic Lateral Sclerosis patients (ALS-CSF) induces neurodegenerative changes in motor neurons and gliosis in sporadic ALS models. Search for identification of toxic factor(s) in CSF revealed an enhancement in the level and enzyme activity of chitotriosidase (CHIT-1). Here, we have investigated its upregulation in a large cohort of samples and more importantly its role in ALS pathogenesis in a rat model.Methods: CHIT-1 level in CSF samples from ALS (n=158), non-ALS (n=12) and normal (n=48) subjects were measured using ELISA. Enzyme activity was also assessed (ALS, n=56; non-ALS, n=10 and normal-CSF, n=45). Recombinant CHIT-1 was intrathecally injected into Wistar rat neonates. Lumbar spinal cord sections were stained for Iba1, Glial Fibrillary Acidic Protein and Choline Acetyl Transferase to identify microglia, astrocytes and motorneurons respectively after 48hrs of injection. Levels of tumor necrosis factor-α and interleukin-6 was measured by ELISA.Findings: CHIT-1 level in ALS-CSF samples was increased by twenty folds and it can distinguish ALS patients with a sensitivity of 87% and specificity of 83·3% at a cut off level of 1405·43 pg/ml. Enzyme activity of CHIT-1 was also fifteen folds higher in ALS-CSF and has a sensitivity of 80·4% and specificity of 80% at cut off value of 0·1077989μmol/μl/min. Combining CHIT-1 level and activity together gave a positive predictive value of 97·78% and negative predictive value of 100%. Administration of CHIT-1 increased microglial numbers and astrogliosis in the ventral horn with a concomitant increase in the levels of pro-inflammatory cytokines. Amoeboid shaped microglial and astroglial cells were also present around the central canal. CHIT-1 administration also resulted in the reduction of motorneurons.Conclusions: CHIT-1, an early diagnostic biomarker of sporadic ALS activates glia priming them to attain a toxic phenotype resulting in neuroinflammation leading to motor neuronal death.

Chitotriosidase 1 in the cerebrospinal fluid as a putative biomarker for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) progression

“…This suggests that CHIT1 was intrathecally produced. In ALS, controversial results indicate that only CSF CHIT1 levels or both CSF and serum levels are useful as disease biomarker (43,44). However, the lack of paired CSF and serum samples in these studies might limited to obtain consistent conclusions.…”

“…Altered levels of CHIT1 in the CSF have been shown as a biomarker for other neurodegenerative disorders, such as Alzheimer's disease, amyotrophic lateral sclerosis (ALS), and multiple sclerosis (41)(42)(43). In ALS, it was observed an association between CSF CHIT1 levels and both disease severity and progression (44,45). In addition, CHIT1 intrathecal administration in a rat experimental model induced microglia and astrocyte activation leading to neuroinflammation and neuronal loss in the spinal cord (44).…”

“…In ALS, it was observed an association between CSF CHIT1 levels and both disease severity and progression (44,45). In addition, CHIT1 intrathecal administration in a rat experimental model induced microglia and astrocyte activation leading to neuroinflammation and neuronal loss in the spinal cord (44). Similar findings were observed in patients with multiple sclerosis with rapid neurological deterioration, which displayed higher CSF CHIT1 levels in addition to other markers of microglial activity, such as TREM-2 (triggering receptor expressed on myeloid cells 2) and CH3L1 (chitinase-3-like protein 1 precursor) (41).…”