神经酰胺三己糖苷酶，肌萎缩侧索硬化症的生物标志物，通过神经炎症加重脊髓运动神经元的神经退行性变。
Chitotriosidase, a biomarker of amyotrophic lateral sclerosis, accentuates neurodegeneration in spinal motor neurons through neuroinflammation.
机构信息
Department of Neurophysiology, National Institute of Mental Health and Neuro Sciences, Hosur Road, Bengaluru, 560 029, India.
Department of Clinical Neuroscience, National Institute of Mental Health and Neuro Sciences, Hosur Road, Bengaluru, 560 029, India.
出版信息
J Neuroinflammation. 2020 Aug 6;17(1):232. doi: 10.1186/s12974-020-01909-y.
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 h of injection. Levels of tumour necrosis factor-α and interleukin-6 were measured by ELISA.
FINDINGS
CHIT-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.
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.
背景
来自肌萎缩侧索硬化症（ALS）患者的脑脊液（ALS-CSF）会导致散发性 ALS 模型中的运动神经元神经退行性变和神经胶质增生。在 CSF 中寻找有毒因子的过程中，发现壳三糖苷酶（CHIT-1）的水平和酶活性增强。在这里，我们在大量样本中研究了其上调情况，更重要的是在大鼠模型中研究了其在 ALS 发病机制中的作用。
方法
采用 ELISA 法测定 158 例 ALS 患者（ALS 组）、12 例非 ALS 患者（非 ALS 组）和 48 例正常对照者（正常组）脑脊液中 CHIT-1 水平，同时检测 56 例 ALS 患者（ALS 组）、10 例非 ALS 患者（非 ALS 组）和 45 例正常 CSF（正常组）中的酶活性。将重组 CHIT-1 鞘内注射至 Wistar 新生大鼠，注射后 48 小时对脊髓腰段进行染色，分别用 Iba1、胶质纤维酸性蛋白和胆碱乙酰转移酶鉴定小胶质细胞、星形胶质细胞和运动神经元。采用 ELISA 法检测肿瘤坏死因子-α和白细胞介素-6 水平。
结果
ALS-CSF 样本中 CHIT-1 水平增加了 20 倍，其在 1405.43pg/ml 截点水平时，诊断 ALS 的敏感度为 87%，特异度为 83.3%。CHIT-1 酶活性在 ALS-CSF 中也增加了 15 倍，在 0.1077989μmol/μl/min 截点时，敏感度为 80.4%，特异度为 80%。联合检测 CHIT-1 水平和活性时，阳性预测值为 97.78%，阴性预测值为 100%。CHIT-1 给药后，腹角内小胶质细胞数量和星形胶质细胞增生，促炎细胞因子水平升高。中央管周围还存在阿米巴样小胶质细胞和星形胶质细胞。CHIT-1 给药还导致运动神经元减少。
结论
CHIT-1 是散发性 ALS 的早期诊断生物标志物，可激活神经胶质细胞，使其获得毒性表型，导致神经炎症，从而导致运动神经元死亡。
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