Serum levels of neuropeptides CRH, substance P, and hemokinin-1 were significantly elevated in fibromyalgia patients alongside inflammatory cytokines IL-6 and TNF, suggesting that neuropeptide-driven mast cell activation contributes to fibromyalgia symptoms.
Substance P 3.25× higher in fibromyalgia0.39 vs 0.12 ng/ml (P<0.0001) — the most dramatically elevated neuropeptide among three that were significantly increased
What the researchers found
Three neuropeptides were significantly elevated in fibromyalgia serum: CRH (0.82 vs 0.49 ng/ml, P = 0.026), substance P (0.39 vs 0.12 ng/ml, P < 0.0001), and hemokinin-1 (7.98 vs 5.71 ng/ml, P = 0.002). SP and HK-1 levels were positively correlated (Pearson r = 0.45, P = 0.002).
Inflammatory cytokines IL-6 (2.97 vs 1.79 pg/ml, P = 0.029) and TNF (0.92 vs 0.69 pg/ml, P = 0.006) were also elevated. Conversely, IL-31 and IL-33 were significantly lower in fibromyalgia patients (P = 0.0001 and P = 0.044). Neurotensin levels showed no difference. The authors connect these findings to their prior work showing CRH and SP stimulate IL-6 and TNF release from mast cells.
Why it matters
Fibromyalgia affects 2-8% of the population and lacks reliable biomarkers or targeted treatments. This study identifies a specific neuropeptide-mast cell-cytokine pathway that could explain the widespread pain and inflammation in fibromyalgia. If confirmed, this pathway offers both diagnostic biomarker candidates and therapeutic targets — treatments blocking these neuropeptides or stabilizing mast cells could address the underlying biology rather than just managing symptoms.
How the study worked
Researchers measured serum concentrations of neuropeptides (CRH, substance P, hemokinin-1, neurotensin) and inflammatory cytokines (IL-6, TNF, IL-31, IL-33) in fibromyalgia patients and healthy controls using biochemical assays. Statistical comparisons between groups used appropriate tests, and Pearson correlation analysis assessed relationships between biomarkers.
What this study cannot tell us
The specific sample size is not detailed in the abstract, limiting assessment of statistical power. This is a cross-sectional observational study, so causality cannot be established — elevated neuropeptides could be a cause, consequence, or correlate of fibromyalgia. Serum measurements may not reflect tissue-level neuropeptide concentrations at pain sites. The study did not control for medications that may affect neuropeptide or cytokine levels.
How to read the evidence
This is a cross-sectional biomarker study comparing fibromyalgia patients to healthy controls. While the statistical findings are strong (multiple P-values well below 0.05), the observational design cannot establish causality. The mechanistic interpretation linking neuropeptides to mast cell activation draws on prior work but was not directly tested in this study.
When this study was published
Published in 2016, this study established foundational evidence for the neuropeptide-mast cell hypothesis in fibromyalgia. Subsequent research has continued to explore this pathway, making the findings a starting point for an active area of investigation.
The bigger picture
This study fits into a growing body of evidence linking neurogenic inflammation — driven by neuropeptides — to chronic pain conditions like fibromyalgia. The mast cell connection is particularly intriguing because mast cells sit at the interface of the nervous and immune systems. Understanding this neuroimmune crosstalk could not only advance fibromyalgia treatment but also shed light on other conditions involving neuropeptide-driven inflammation, such as chronic fatigue syndrome and interstitial cystitis.
Questions still open
- Could neuropeptide or mast cell-targeted therapies improve pain outcomes in fibromyalgia patients?
- Do neuropeptide levels correlate with fibromyalgia symptom severity, and could they serve as treatment response biomarkers?
- Is the neuropeptide-mast cell pathway specific to fibromyalgia or shared with other chronic pain syndromes?
Common questions
What is the connection between neuropeptides and fibromyalgia pain?
Could these findings lead to new fibromyalgia treatments?
Read the original research
Neuropeptides CRH, SP, HK-1, and Inflammatory Cytokines IL-6 and TNF Are Increased in Serum of Patients with Fibromyalgia Syndrome, Implicating Mast Cells.
The Journal of pharmacology and experimental therapeutics, 356(3), 664-72
Citation
Tsilioni, Irene; Russell, Irwin J; Stewart, Julia M; Gleason, Rae M; Theoharides, Theoharis C. (2016). Neuropeptides CRH, SP, HK-1, and Inflammatory Cytokines IL-6 and TNF Are Increased in Serum of Patients with Fibromyalgia Syndrome, Implicating Mast Cells.. The Journal of pharmacology and experimental therapeutics, 356(3), 664-72. https://doi.org/10.1124/jpet.115.230060