Sleep disturbances and severe stress as glial activators: key targets for treating central sensitization in chronic pain patients?

ABSTRACT

Introduction: The mechanism of sensitization of the central nervous system partly explains the chronic pain experience in many patients, but the etiological mechanisms of this central nervous system dysfunction are poorly understood. Recently, an increasing number of studies suggest that aberrant glial activation takes part in the establishment and/or maintenance of central sensitization.

Areas covered: This review focused on preclinical work and mostly on the neurobiochemistry studied in animals, with limited human studies available. Glial overactivation results in a low-grade neuroinflammatory state, characterized by high levels of BDNF, IL-1β, TNF-α, which in turn increases the excitability of the central nervous system neurons through mechanisms like long-term potentiation and increased synaptic efficiency. Aberrant glial activity in chronic pain might have been triggered by severe stress exposure, and/or sleeping disturbances, each of which are established initiating factors for chronic pain development.

Expert opinion: Potential treatment avenues include several pharmacological options for diminishing glial activity, as well as conservative interventions like sleep management, stress management and exercise therapy. Pharmacological options include propentofylline, minocycline, β -adrenergic receptor antagonists, and cannabidiol. Before translating these findings from basic science to clinical settings, more human studies exploring the outlined mechanisms in chronic pain patients are needed.

KEYWORDS:

• Pain
• fibromyalgia
• low back pain
• sleep
• stress
• neuroinflammation

Article highlights

• An increasing amount of animal research data supports the idea of aberrant glial activity as a potential underlying, even etiological, mechanism of central sensitization.

• A recent human study using positron emission tomography-magnetic resonance imaging (PET/MRI) identified a pattern consistent with brain glial activation in patients with chronic low back pain, and other human cerebrospinal fluid studies support the idea of neural inflammation in chronic pain patients.

• Stress and poor sleep can trigger glial overactivation and subsequent low-grade neuroinflammatory state, characterized by high levels of BDNF, IL-1β, TNF-α, which in turn increases the excitability of the central nervous system neurons through mechanisms like long-term potentiation and increased synaptic efficiency.

• Several potential pharmacological treatment avenues for diminishing glial activity in chronic pain patients are available, including minocycline antibiotics, β-adrenergic receptor antagonists and propentofylline. Human causation and effectiveness studies exploring these pharmacological options are emerging.

• Potential conservative treatment options for normalizing glial activity in chronic pain patients include sleep management (e.g., cognitive behavioral therapy for insomnia), stress management and exercise therapy, but studies examining whether such interventions can actually normalize glial activity in chronic pain patients are needed.

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Acknowledgments

The first author is grateful to Boudewijn Van Houdenhove (MD, PhD), for motivating and inspiring him to explore the role of stress in relation to chronic pain.

Declaration of interest

M. Moens received the Lyrica Independent Investigator Research Award (LIIRA) and received consultancy or speaker honoraria from Medtronic and Pfizer.

Additional information

Funding

K Ickmans, L. Goudman and E. Huysmans are funded by the Applied Biomedical Research Program, Institute for the Agency for Innovation by Science and Technology, Belgium (IWT-TBM project no. 150,180). J. Nijs is holder of the Chair ‘Exercise immunology and chronic fatigue in health and disease’ funded by the Berekuyl Academy /European College for Decongestive Lymphatic Therapy, The Netherlands. A. Polli is a PhD research fellow funded by ME Research UK, a national charity funding biomedical research in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome.