Cerebrospinal fluid proteomics in recent-onset Narcolepsy type 1 reveals activation of the complement system

Front Immunol. 2023 Apr 12:14:1108682. doi: 10.3389/fimmu.2023.1108682. eCollection 2023.

Abstract

Introduction: Narcolepsy type 1 (NT1) is a rare, chronic and disabling neurological disease causing excessive daytime sleepiness and cataplexy. NT1 is characterized pathologically by an almost complete loss of neurons producing the orexin neuropeptides in the lateral hypothalamus. Genetic and environmental factors strongly suggest the involvement of the immune system in the loss of orexin neurons. The cerebrospinal fluid (CSF), secreted locally and surrounding the central nervous system (CNS), represents an accessible window into CNS pathological processes.

Methods: To gain insight into the biological and molecular changes in NT1 patients, we performed a comparative proteomics analysis of the CSF from 21 recent-onset NT1 patients and from two control groups: group 1 with somatoform disorders, and group 2 patients with hypersomnia other than NT1, to control for any potential effect of sleep disturbances on CSF composition. To achieve an optimal proteomic coverage analysis, the twelve most abundant CSF proteins were depleted, and samples were analyzed by nano-flow liquid chromatography tandem mass spectrometry (nano-LC-MS/MS) using the latest generation of hybrid Orbitrap mass spectrometer.

Results and discussion: Our study allowed the identification and quantification of up to 1943 proteins, providing a remarkably deep analysis of the CSF proteome. Interestingly, gene set enrichment analysis indicated that the complement and coagulation systems were enriched and significantly activated in NT1 patients in both cohorts analyzed. Notably, the lectin and alternative complement pathway as well as the downstream lytic membrane attack complex were congruently increased in NT1. Our data suggest that the complement dysregulation in NT1 patients can contribute to immunopathology either by directly promoting tissue damage or as part of local inflammatory responses. We therefore reveal an altered composition of the CSF proteome in NT1 patients, which points to an ongoing inflammatory process contributed, at least in part, by the complement system.

Keywords: cerebrospinal fluid; coagulation system; complement system; immune response; narcolepsy type 1; neuroimmunology; proteomics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Complement System Proteins
  • Humans
  • Narcolepsy*
  • Orexins
  • Proteome
  • Proteomics
  • Tandem Mass Spectrometry*

Substances

  • Orexins
  • Proteome
  • Complement System Proteins

Grants and funding

The work was supported by Inserm, CNRS, Institut Universitaire de France and grants from Agence Nationale pour la Recherche (CE14-14066; CE17-0014), and ERA-Net Narcomics. The funders had no role in the design and interpretation of the study.