Division of Neuropediatrics and Social Pediatrics, Department of Pediatrics, RWTH Aachen University Hospital, Aachen, Germany.
Helmholtz Institute for Biomedical Engineering, Biointerface Laboratory, RWTH Aachen University Hospital, Aachen, Germany.
PLoS One. 2022 Oct 7;17(10):e0268592. doi: 10.1371/journal.pone.0268592. eCollection 2022.
Fetuin-A is a liver derived plasma protein showing highest serum concentrations in utero, preterm infants, and neonates. Fetuin-A is also present in cerebrospinal fluid (CSF). The origin of CSF fetuin-A, blood-derived via the blood-CSF barrier or synthesized intrathecally, is presently unclear. Fetuin-A prevents ectopic calcification by stabilizing calcium and phosphate as colloidal calciprotein particles mediating their transport and clearance. Thus, fetuin-A plays a suppressive role in inflammation. Fetuin-A is a negative acute-phase protein under investigation as a biomarker for multiple sclerosis (MS). Here we studied the association of pediatric inflammatory CNS diseases with fetuin-A glycosylation and phosphorylation. Paired blood and CSF samples from 66 children were included in the study. Concentration measurements were performed using a commercial human fetuin-A/AHSG ELISA. Of 60 pairs, 23 pairs were analyzed by SDS-PAGE following glycosidase digestion with PNGase-F and Sialidase-AU. Phosphorylation was analyzed in 43 pairs by Phos-TagTM acrylamide electrophoresis following alkaline phosphatase digestion. Mean serum and CSF fetuin-A levels were 0.30 ± 0.06 mg/ml and 0.644 ± 0.55 μg/ml, respectively. This study showed that serum fetuin-A levels decreased in inflammation corroborating its role as a negative acute-phase protein. Blood-CSF barrier disruption was associated with elevated fetuin-A in CSF. A strong positive correlation was found between the CSF fetuin-A/serum fetuin-A quotient and the CSF albumin/serum albumin quotient, suggesting predominantly transport across the blood-CSF barrier rather than intrathecal fetuin-A synthesis. Sialidase digestion showed increased asialofetuin-A levels in serum and CSF samples from children with neuroinflammatory diseases. Desialylation enhanced hepatic fetuin-A clearance via the asialoglycoprotein receptor thus rapidly reducing serum levels during inflammation. Phosphorylation of fetuin-A was more abundant in serum samples than in CSF, suggesting that phosphorylation may regulate fetuin-A influx into the CNS. These results may help establish Fetuin-A as a potential biomarker for neuroinflammatory diseases.
胎球蛋白 A 是一种肝脏来源的血浆蛋白，在子宫内、早产儿和新生儿中血清浓度最高。胎球蛋白 A 也存在于脑脊液 (CSF) 中。CSF 胎球蛋白 A 的来源，是通过血脑屏障从血液中进入，还是在鞘内合成，目前尚不清楚。胎球蛋白 A 通过将钙和磷酸盐稳定为胶体钙蛋白颗粒来防止异位钙化，从而介导其转运和清除。因此，胎球蛋白 A 在炎症中发挥抑制作用。胎球蛋白 A 是一种负急性期蛋白，正在作为多发性硬化症 (MS) 的生物标志物进行研究。在这里，我们研究了儿科炎症性中枢神经系统疾病与胎球蛋白 A 糖基化和磷酸化的关系。本研究纳入了 66 名儿童的配对血液和 CSF 样本。使用商业的人胎球蛋白 A/AHSG ELISA 进行浓度测量。在 60 对样本中，有 23 对在经 PNGase-F 和 Sialidase-AU 糖苷酶消化后进行 SDS-PAGE 分析。在经碱性磷酸酶消化后进行 Phos-TagTM 丙烯酰胺电泳分析了 43 对样本的磷酸化。血清和 CSF 胎球蛋白 A 水平的平均值分别为 0.30±0.06mg/ml 和 0.644±0.55μg/ml。本研究表明，炎症时血清胎球蛋白 A 水平降低，证实了其作为负急性期蛋白的作用。血脑屏障破坏与 CSF 中胎球蛋白 A 升高有关。CSF 胎球蛋白 A/血清胎球蛋白 A 比值与 CSF 白蛋白/血清白蛋白比值呈强正相关，提示主要通过血脑屏障转运，而不是鞘内合成胎球蛋白 A。唾液酸酶消化显示，神经炎症性疾病患儿的血清和 CSF 样本中存在更多的去唾液酸化胎球蛋白 A。去唾液酸化增强了胎球蛋白 A 通过去唾液酸糖蛋白受体的清除，从而在炎症期间迅速降低血清水平。胎球蛋白 A 的磷酸化在血清样本中比在 CSF 中更为丰富，这表明磷酸化可能调节胎球蛋白 A 进入中枢神经系统。这些结果可能有助于将胎球蛋白 A 确立为神经炎症性疾病的潜在生物标志物。
