Fibromyalgia patients show elevated levels of neuropeptides substance P and hemokinin-1, and the authors propose that thalamic mast cells releasing these peptides along with CGRP drive neuroinflammation and chronic pain.
Elevated substance P and HK-1 in FMSFibromyalgia patients had significantly increased blood levels of the neuropeptides substance P and hemokinin-1 along with pro-inflammatory cytokines, supporting a neuroinflammatory mechanism driven by mast cell-released peptides.
What the researchers found
Previous work by this group found that fibromyalgia patients had significantly increased serum levels of substance P, hemokinin-1 (HK-1), IL-6, and TNF compared to sedentary controls.
Based on these findings, the authors propose a mechanistic hypothesis: mast cells in the thalamus release neuro-sensitizing molecules — including histamine, IL-1β, IL-6, TNF, CGRP, HK-1, and substance P — that activate thalamic pain-processing neurons either directly or via microglial stimulation. This creates a neuroinflammatory cycle that could explain the chronic, widespread pain of fibromyalgia. They suggest that inhibiting mast cell activation could be a novel therapeutic approach.
Why it matters
Fibromyalgia affects an estimated 2-4% of the population globally, predominantly women, yet there is no clearly defined pathogenesis and treatments are often inadequate. This hypothesis directly connects measurable neuropeptide abnormalities (substance P, CGRP, hemokinin-1) to a specific cellular mechanism (thalamic mast cell activation), potentially opening new therapeutic avenues. Mast cell stabilizers already exist and are used for other conditions, making this hypothesis testable with existing drugs.
How the study worked
This paper reviews the authors' previous clinical findings (elevated neuropeptides and cytokines in fibromyalgia patients vs. controls) and synthesizes them with existing literature on mast cell biology, neuroinflammation, and pain signaling to propose a mechanistic model. It is a hypothesis-driven review rather than a primary experimental study.
What this study cannot tell us
This is primarily a hypothesis paper that proposes a mechanism based on the authors' previous findings and existing literature. The thalamic mast cell hypothesis has not been directly tested with experiments demonstrating causation. The elevated neuropeptide levels in serum may not reflect brain concentrations. The role of mast cells in the thalamus specifically in fibromyalgia has not been confirmed with human brain tissue studies. The hypothesis, while plausible, remains to be validated.
How to read the evidence
This is a hypothesis and review paper that synthesizes the authors' clinical findings with existing literature. While the elevated neuropeptide data comes from their prior clinical study, the proposed mast cell mechanism in the thalamus is theoretical and requires experimental validation. The evidence is suggestive but not confirmatory.
When this study was published
Published in 2019, this paper reflects growing interest in neuroinflammation as a driver of fibromyalgia. Since then, research into mast cell involvement in chronic pain and the role of CGRP in conditions beyond migraine has continued to expand.
The bigger picture
The role of neuropeptides in chronic pain conditions is gaining increasing attention. Substance P was one of the first neuropeptides linked to pain, and CGRP is now the target of successful migraine drugs. This paper connects these peptides to fibromyalgia through a mast cell-mediated mechanism, bridging immunology and neurology. The growing recognition that chronic pain conditions involve neuroinflammation rather than simple nerve dysfunction is reshaping pain medicine and may eventually yield more targeted treatments.
Questions still open
- Can mast cell stabilizers (like cromolyn sodium or ketotifen) reduce pain symptoms in fibromyalgia clinical trials?
- Are thalamic mast cell numbers or activity actually increased in fibromyalgia patients compared to healthy controls?
- Would anti-CGRP therapies (already used for migraine) also benefit fibromyalgia patients through the same neuroinflammatory mechanism?
Common questions
What are neuropeptides and how do they relate to fibromyalgia pain?
Could mast cell-targeting drugs help treat fibromyalgia?
Read the original research
Mast Cells, Neuroinflammation and Pain in Fibromyalgia Syndrome.
Frontiers in cellular neuroscience, 13, 353
Citation
Theoharides, Theoharis C; Tsilioni, Irene; Bawazeer, Mona. (2019). Mast Cells, Neuroinflammation and Pain in Fibromyalgia Syndrome.. Frontiers in cellular neuroscience, 13, 353. https://doi.org/10.3389/fncel.2019.00353