EAN 2026 | PACAP-38 is increased in the tear fluid of patients with migraine

PACAP-38 is a neuropeptide released from trigeminal nerve endings and from parasympathetic fibers, and both trigeminal fibers and parasympathetic fibers innervate the lacrimal gland. So we thought we could find this peptide in the tear fluid. PACAP-38 has been measured also in plasma with inconsistent results, with some studies finding higher levels in patients with migraine compared to controls and other studies finding no differences. So we collected tear fluid with a Schirmer test, so basically placing a Schirmer strip in the lower eyelid for a few seconds, and we assayed PACAP-38 through ELISA. We found significantly higher levels of PACAP-38 in the tear fluid of patients with migraine compared to healthy controls. Roughly 22 picograms per milliliter in patients with migraine and four in controls. And also, we defined a cutoff of PACAP-38 in the tear fluid of two picograms per milliliter that could distinguish patients with migraine and controls with a fair sensitivity and specificity of about around 70%. So we found this molecule for the first time in the tear fluid, and this can have important implications because right now we have in the pipeline monoclonal antibodies anti-PACAP. So these molecules can serve as biomarkers that can help us to stratify patients and maybe can inform us in the future treatment strategies and possibly response to novel targeted therapeutic strategies.

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