Prodynorphin and Proenkephalin in Cerebrospinal Fluid of Sporadic Creutzfeldt-Jakob Disease

Abstract

Proenkephalin (PENK) and prodynorphin (PDYN) are endogenous opioid peptides mainly produced in the striatum and, to a lesser extent, in the cerebral cortex. Dysregulated metabolism and altered cerebrospinal fluid (CSF) levels of PENK and PDYN have been described in several neurodegenerative diseases. However, no study to date investigated these peptides in the CSF of sporadic Creutzfeldt-Jakob disease (sCJD). Using liquid chromatography-multiple reaction monitoring mass spectrometry, we evaluated the CSF PDYN- and PENK-derived peptide levels in 25 controls and 63 patients with sCJD belonging to the most prevalent molecular subtypes (MM(V)1, VV2 and MV2K). One of the PENK-derived peptides was significantly decreased in each sCJD subtype compared to the controls without a difference among subtypes. Conversely, PDYN-derived peptides were selectively decreased in the CSF of sCJD MV2K, a subtype with a more widespread overall pathology compared to the sCJD MM(V)1 and the VV2 subtypes, which we confirmed by semiquantitative analysis of cortical and striatal neuronal loss and astrocytosis. In sCJD CSF PENK and PDYN were associated with CSF biomarkers of neurodegeneration but not with clinical variables and showed a poor diagnostic performance. CSF PDYN and PENK-derived peptides had no significant diagnostic and prognostic values in sCJD; however, the distinct marker levels between molecular subtypes might help to better understand the basis of phenotypic heterogeneity determined by divergent neuronal targeting.

Keywords: Creutzfeldt–Jakob disease; biomarkers; mass spectrometry; opioid peptides; prion disease; prodynorphin; proenkephalin.

Figure 1

CSF levels of PENK and PDYN in sCJD, its subtypes and controls. Levels were determined by the measurement of two PDYN peptides ([SVG...LAR] and [FLP...STR]) and two PENK peptides ([DAE...LLK] and [FAE...YSK]) by targeted liquid chromatography-tandem mass spectrometry. The median and interquartile range are shown for the ratio of light peptides to spiked heavy labelled peptides (L/H). Kruskal–Wallis test and Dunn’s post hoc test. Comparisons of biomarker levels between sCJD and controls are shown in subfigures (A–D), whereas comparisons among sCJD subtypes and controls are shown in subfigures (E–H).

Figure 2

Semiquantitative neuropathological analysis of neuronal loss and astrogliosis in the striatum and cortex of sCJD subtypes MM(V)1, MV2K and VV2. Comparisons between sCJD subtypes MM(V)1, MV2K and VV2 concerning the score of neuronal loss and astrogliosis in the striatum and cerebral cortex. Kruskal–Wallis test and Dunn’s post hoc test.