Biomarkers & Research, Nordic Bioscience, Herlev, Denmark.
Department of Cardiology B, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
PLoS One. 2019 Nov 6;14(11):e0224633. doi: 10.1371/journal.pone.0224633. eCollection 2019.
Blood levels of Glial Fibrillary Acidic protein (GFAP) reflect processes associated with different types of CNS injury. Evidence suggests that GFAP is cleaved by caspases during CNS injury, hence positioning GFAP fragments as potential biomarkers of injury-associated processes. We set out to develop an assay detecting the neo-epitope generated by caspase-6 cleavage of GFAP (GFAP-C6), and to assess the ability of GFAP-C6 to reflect pathological processes in patients suffering a cardiac arrest and subsequent global cerebral ischemia. Anti-GFAP-C6 antibodies recognized their specific target sequence, and dilution and spike recoveries in serum were within limits of ±20% reflecting high precision and accuracy of measurements. Intra- and inter-assay CVs were below limits of 10% and 15%, respectively. Serological levels of GFAP-C6 were significantly elevated 72 hours after CA (Mean±SD) (20.39±10.59 ng/mL) compared to time of admission (17.79±10.77 ng/mL, p<0.0001), 24 hours (17.40±7.99 ng/mL, p<0.0001) and 48 hours (17.87±8.56 ng/mL, p<0.0001) after CA, but were not related to neurological outcome at day 180. GFAP-C6 levels at admission, 24, 48, and 72 hours after cardiac arrest correlated with two proteolytic fragments of tau, tau-A (r = 0.30, r = 0.40, r = 0.50, r = 0.53, p < 0.0001) and tau-C (r = 54, r = 0.48, r = 0.55, r = 0.54, p < 0.0001), respectively. GFAP-C6 levels did not correlate with other markers of CNS damage; total tau, NSE and S100B. In conclusion, we developed the first assay detecting a caspase-6 cleaved fragment of GFAP in blood. Increased levels at 72 hours after cardiac arrest as well as moderate correlations between GFAP-C6 and two other blood biomarkers of neurodegeneration suggest the ability of GFAP-C6 to reflect pathological processes of the injured brain. Investigations into the potential of GFAP-C6 in other types of CNS injury are warranted.
血液中神经胶质纤维酸性蛋白（GFAP）的水平反映了与中枢神经系统损伤类型相关的过程。有证据表明，GFAP 在中枢神经系统损伤时被半胱天冬酶切割，因此 GFAP 片段定位为潜在的损伤相关过程的生物标志物。我们着手开发一种检测半胱天冬酶-6 切割 GFAP 产生的新表位（GFAP-C6）的测定方法，并评估 GFAP-C6 反映心脏骤停和随后全脑缺血患者病理过程的能力。抗 GFAP-C6 抗体识别其特异性靶序列，血清中的稀释和加标回收率在±20%的范围内，反映了测量的高精度和准确性。内和间测定变异系数分别低于 10%和 15%。与入院时（17.79±10.77ng/mL，p<0.0001）、心脏骤停后 24 小时（17.40±7.99ng/mL，p<0.0001）和 48 小时（17.87±8.56ng/mL，p<0.0001）相比，CA 后 72 小时（20.39±10.59ng/mL）血清中 GFAP-C6 的水平显著升高，但与 180 天的神经功能结局无关。心脏骤停后入院时、24 小时、48 小时和 72 小时的 GFAP-C6 水平与 tau 的两种蛋白水解片段 tau-A（r = 0.30，r = 0.40，r = 0.50，r = 0.53，p<0.0001）和 tau-C（r = 0.54，r = 0.48，r = 0.55，r = 0.54，p<0.0001）相关。GFAP-C6 水平与其他中枢神经系统损伤标志物；总 tau、NSE 和 S100B 不相关。总之，我们开发了检测血液中半胱天冬酶-6 切割 GFAP 片段的第一种测定方法。心脏骤停后 72 小时水平升高以及 GFAP-C6 与另外两种神经退行性变血液生物标志物之间的中度相关性表明，GFAP-C6 能够反映受损大脑的病理过程。需要进一步研究 GFAP-C6 在其他类型的中枢神经系统损伤中的潜力。
