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

• DOI: 10.21203/rs.2.21147/v1
• Publication Date: 2020-01-17T20:49:15Z
• Authors: Anu Mary Varghese; Mausam Ghosh; Savita Kumari Bhagat; K Vijayalakshmi; Veeramani Preethi...; Seena Vengalil; Pradeep-Chandra-R...; Saraswati Nashi; Kiran Polavarapu; Meenakshi Sharma; Rupinder Singh Dh...; Mariamma Philip; Atchayaram Nalini; Phalguni Anand Al...; Talakad N Sathyap...; Trichur R Raju
• Keywords: Adult; Male; Motor Neurons; Research; Amyotrophic Lateral Sclerosis; Biomarker; Middle Aged; Amyotrophic lateral sclerosis; Rats; Hexosaminidases; Neuroinflammation; Spinal Cord; Glia; Nerve Degeneration; Animals; Encephalitis; Humans; Female; Neurology. Diseases of the nervous system; Microglia; Neurodegeneration; Rats, Wistar; RC346-429; Biomarkers; Chitotriosidase

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 motor neurons respectively after 48 hrs 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 motor neurons.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.