Chitotriosidase, a biomarker of amyotrophic lateral sclerosis, accentuates neurodegeneration in spinal motor neurons through neuroinflammation

Anu Mary Varghese,Trichur R Raju,Veeramani Preethish-Kumar,Savita Kumari Bhagat,Rupinder Singh Dhaliwal,Mausam Ghosh,Meenakshi Sharma,K Vijayalakshmi,Atchayaram Nalini,Phalguni Anand Alladi,Saraswati Nashi,Seena Vengalil,Pradeep-Chandra-Reddy Chevula,Mariamma Philip,Talakad N Sathyaprabha,Kiran Polavarapu

doi:10.1186/s12974-020-01909-y

Abstract

BackgroundCerebrospinal 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.MethodsCHIT-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 motor neurons respectively after 48 h of injection. Levels of tumour necrosis factor-α and interleukin-6 were measured by ELISA.FindingsCHIT-1 level in ALS-CSF samples was increased by 20-fold 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 15-fold higher in ALS-CSF and has a sensitivity of 80.4% and specificity of 80% at cut off value of 0.1077989 μmol/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 motor neurons.ConclusionsCHIT-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.

Highlights

Cerebrospinal fluid from amyotrophic lateral sclerosis patients (ALS-CSF) induces neurodegenerative changes in motor neurons and gliosis in sporadic ALS models
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
Diagnosis of amyotrophic lateral sclerosis (ALS), a non-cell autonomous neurodegenerative disorder marked by degeneration of motor neurons along with muscular atrophy, is still challenging as the symptom development could be delayed during initial phase and may overlap with other neurodegenerative disorders [1,2,3,4]

Summary

Introduction

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). Diagnosis of amyotrophic lateral sclerosis (ALS), a non-cell autonomous neurodegenerative disorder marked by degeneration of motor neurons along with muscular atrophy, is still challenging as the symptom development could be delayed during initial phase and may overlap with other neurodegenerative disorders [1,2,3,4]. We were the first to report that chitotriosidase (CHIT-1) can be a putative biomarker for ALS, as the level and activity of CHIT-1 was markedly increased in cerebrospinal fluid of ALS patients (ALS-CSF) [5]. While some studies suggest that it is toxic, others assign it a protective role in the human system [8, 9]

Methods

Results

Conclusion