CSF SerpinA1 in Creutzfeldt-Jakob disease and frontotemporal lobar degeneration

Abstract

Objective: SerpinA1 (alpha-1 antitrypsin) is an acute inflammatory protein, which seems to play a role in neurodegeneration and neuroinflammation. In Alzheimer's disease and synucleinopathies, SerpinA1 is overexpressed in the brain and the cerebrospinal fluid (CSF) showing abnormal patterns of its charge isoforms. To date, no comprehensive studies explored SerpinA1 CSF isoforms in Creutzfeldt-Jakob disease (CJD) and frontotemporal lobar degeneration (FTLD).

Methods: Using a capillary isoelectric focusing immunoassay, we analyzed CSF SerpinA1 isoforms in control cases (n = 31) and patients with a definite or probable diagnosis of CJD (n=77) or FTLD (n = 30), belonging to several disease subtypes.

Results: The overall SerpinA1 signal was significantly higher than in controls in CJD subtypes linked to abnormal prion protein (PrP^Sc ) type 1, such as sporadic CJD (sCJD) MM(V)1, and in FTLD-TDP. Moreover, CJD linked to PrP^Sc type 1 and FTLD-TAU groups showed a significant relative increase of acidic and basic isoforms in comparison with controls, thereby forming two distinct SerpinA1 isoform profiles.

Interpretation: CJD linked to PrP^Sc type 1 and FTLD show a differential upregulation and post-translational modifications of CSF SerpinA1. Further studies are needed to clarify whether these findings may reflect a common, albeit disease-specific, pathogenetic mechanism related to neurodegeneration.

Figure 1

Typical CSF electropherograms of SerpinA1 isoforms. The y‐axis depicts the signal in arbitrary units; the x‐axis the isoelectric point (pI). (A) Overlay of a sCJD VV2 (pink) and a control (green) electropherogram. (B) Overlay of a sCJD MV2K (rose) and a control (green) electropherogram. (C) Overlay of a sCJD MM2C (purple) and a control (green) electropherogram. (D) Overlay of a sCJD MM(V)1 (red) and a control electropherogram (green). At variance with the VV2, MV2K, and MM2C profiles, the MM(V)1 electropherogram differs from the control one. Seven [MM(V)1] or six (control) distinct peaks around the pI of 4.5 were detected. Most notably is the difference in the abundance of the acidic isoforms. (E) Overlay of a sCJD VV1 (orange) and a control (green) electropherogram, showing, in the former, the same increase of the acidic isoforms detected in the MM(V)1 cases. (F) Overlay of a FTLD (blue) and a control (green) electropherogram. In the case of FTLD, the most significant difference is in the abundance of the two most basic isoforms. CJD, Creutzfeldt–Jakob disease; FTLD, frontotemporal lobar degeneration; MM(V)1, methionine homozygosity (valine) and disease‐associated prion protein type 1; MM2C, methionine homozygosity and disease‐associated prion protein type 2; MV2K, methionine–valine heterozygosity and disease‐associated prion protein type 2; sCJD, sporadic Creutzfeldt–Jakob disease; VV1, valine homozygosity and disease‐associated prion protein type 1; VV2, valine homozygosity and disease‐associated prion protein type 2.

Figure 2

Results of absolute peak area analysis. (A) Comparison of the total absolute area of the three main cohorts (controls, CJD, FTLD). (B) Comparison between controls and sCJD patients after stratification into sCJD subtypes. (C) Comparison between controls and FTLD patients after stratification into the two FTLD subtypes. Box plots show median concentrations with 25% and 75% percentiles and Tukey whiskers. *P < 0.05, **P < 0.01. CJD, Creutzfeldt–Jakob disease; Con, controls; CU, chemiluminescence unit; FTLD, frontotemporal lobar degeneration; FTLD‐TAU, frontotemporal lobar degeneration with tau pathology; FTLD‐TDP, frontotemporal lobar degeneration with TDP43 pathology; MM(V)1, methionine homozygosity (valine) and disease‐associated prion protein type 1; MV2K, methionine/valine heterozygosity and disease‐associated prion protein type 2; sCJD, sporadic Creutzfeldt–Jakob disease; VV2, valine homozygosity and disease‐associated prion protein type 2.

Figure 3

Results of relative peak area analysis. (A) Comparison of mean relative peak areas of all seven peaks of the three main cohorts (controls, CJD, FTLD). Error bars indicate SEM. (B) Normalized area results for peak 0. (C) Normalized area results for peak 3. (D) Normalized area results for peak 6. Symbols in B, C, and D indicate mean normalized area of peak 0, 3, and 6, respectively. Error bars show the 95% confidence interval. *P < 0.05, **P < 0.01. CJD, Creutzfeldt–Jakob disease; Cons, control; FTLD, frontotemporal lobar degeneration.

Figure 4

Relative peak area analysis for sCJD and FTLD subtypes. (A) Normalized peak area analysis of peak 0 for the sCJD subgroups. (B) Normalized peak area analysis of peak 6 for the FTLD subgroups. Box plots show median concentrations with 25% and 75% percentiles and Tukey whiskers. *P < 0.05, ****P < 0.0001. Con, controls; FTLD, frontotemporal lobar degeneration; FTLD‐TAU, frontotemporal lobar degeneration with tau pathology; FTLD‐TDP, frontotemporal lobar degeneration with TDP43 pathology; MM(V)1, methionine homozygosity (valine) and disease‐associated prion protein type 1; MV2K, methionine/valine heterozygosity and disease‐associated prion protein type 2; sCJD, sporadic Creutzfeldt–Jakob disease; VV2, valine homozygosity and disease‐associated prion protein type 2.