Enhanced levels of fractalkine and HSP60 in cerebrospinal fluid of sporadic amyotrophic lateral sclerosis patients

Abstract

Amyotrophic Lateral Sclerosis (ALS) is a multifactorial neurodegenerative disorder with a significant contribution of non-cell autonomous mechanisms to motor neuronal degeneration. Amongst a plethora of molecules, fractalkine (C-X3-C motif chemokine ligand 1), and Heat Shock Protein 60 (HSP60), are key modulators of microglial activation. The contribution of these molecules in Sporadic ALS (SALS) remains unexplored. To investigate this, fractalkine levels were estimated in Cerebrospinal fluid (CSF) of SALS patients (ALS-CSF; n = 44) by Enzyme-linked Immunosorbent Assay (ELISA) and correlated with clinical parameters including disease severity and duration. CSF HSP60 levels were estimated by Western blotting (ALS-CSF; n = 19). Also, CSF levels of Chitotriosidase-1 (CHIT-1), a microglia-specific neuroinflammatory molecule, were measured and its association, if any, with fractalkine and HSP60 was investigated. Both fractalkine and HSP60 levels were significantly elevated in ALS-CSF. Similar to our earlier observation, CHIT-1 levels were also upregulated. Fractalkine showed a moderate negative correlation with the ALS-Functional Rating Scale (ALSFRS) score indicating its significant rise in mild cases which plateaued in cases with high disease severity. However, no obvious correlation was found between fractalkine, HSP60, and CHIT-1. Our study hints that high fractalkine levels in mild cases might be conferring neuroprotection by combating microglial activation and highlights its importance as a novel therapeutic target for SALS. On the other hand, significantly enhanced levels of HSP60, a pro-inflammatory molecule, hint towards its role in accentuating microgliosis, although, it doesn’t act synergistically with CHIT-1. Our study suggests that fractalkine and HSP60 act independently of CHIT-1 to suppress and accentuate neuroinflammation, respectively.

Keywords:

• Fractalkine
• HSP60
• sporadic amyotrophic lateral sclerosis
• cerebrospinal fluid
• chitotriosidase-1
• neuroinflammation

Acknowledgements

The authors immensely thank Mr. Rahul Venugopal, Ph.D. scholar and Dr. B.N. Srikumar, Additional Professor, Department of Neurophysiology for their contribution to statistical analysis of the data. We thank Mr. Punith V. Shivapura and Mr. Harshith V., Integrated B.Sc.-M.Sc. Biological Sciences students from Bangalore University for their contributions to HSP60 Western Blotting during their short-term training program.

The study was reviewed and approved by “The Institutional Human Ethics Committee – NIMHANS IEC”, approval number (No. NIMH/DO/17^th ETHICS SUB-COMMITTEE (BS) Meeting/2016 dated 26.09.2016) and CSF samples were collected from patients with their written informed consent.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Rashmi Savant collected samples, performed the experiments, analysed, and wrote the manuscript. Raj Kumar Pradhan performed the experiments, analysed and contributed to writing the manuscript. Savita Bhagat collected samples and performed the experiments. Anu Mary Varghese collected samples, performed the experiments and analysed the data. Atchayaram Nalini and Seena Vengalil enrolled patients with ALS, performed clinical evaluations, and provided ALS-CSF. Talakad N. Sathyaprabha facilitated obtaining control CSF samples and critically evaluated the manuscript. Trichur R. Raju obtained funding for a part of the study, supervised the study, and critically reviewed the manuscript. K. Vijayalakshmi conceptualized the project, designed the study, obtained funding, supervised the study, analysed and wrote the manuscript.

Data availability statement

All data generated or analysed during this study are included in this article. Further enquiries can be directed to the corresponding author.

Additional information

Funding

The study was funded by the Department of Biotechnology, Govt. of India (BT/PR19944/BIC/101/880/2016). Trichur R. Raju was funded by A.S. Paintal Distinguished Scientific Chair by ICMR, Govt. of India. Savita Bhagat and Anu Mary Varghese were funded by Indian Council for Medical Research, Government of India (ICMR; No.5/4-5/128/Neuro/CAR/2013-NCD-I). Rashmi Savant received senior research fellowship from the University Grants Commission (UGC)/Council of Scientific and Industrial Research (CSIR) fellowship scheme, Government of India.