Tear levels of neuropeptides increase after specific allergen challenge in allergic conjunctivitis.
OBJECTIVE
Growing evidence is showing a role of neurogenic inflammation in allergic reactions, with sensory and autonomic nerve fibers releasing neuromediators, which may actively participate in the allergic inflammatory cascade. Although the cornea is the most densely innervated tissue of the human body, little is known on the role of neuromediators at the ocular surface. In this study, we aimed at evaluating the role of substance P (SP), calcitonine gene related peptide (CGRP), neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) in allergic reactions of the ocular surface.


METHODS
Fifteen patients with allergic conjunctivitis (6 female, 9 male, mean age 30±8 years) in non-active phase, and 10 age-matched healthy subjects were included in this study. The conjunctival provocation test (CPT) with allergen was performed in all allergic patients and in 5 healthy subjects. Tear samples were collected and the tear content of VIP, NPY, CGRP, and SP was measured by ELISA at baseline and after CPT. The Mann-Whitney U-test and Wilcoxon test were used to compare neuromediator tear levels.


RESULTS
No significant differences in neuropeptide tear levels were observed between healthy and allergic patients in non-active phase. CPT induced conjunctival hyperemia and itching in all allergic patients, while no reaction was observed in the control eyes and in healthy subjects. In allergic patients SP, CGRP, and VIP, but not NPY, were significantly higher after CPT as compared to baseline (SP: 3.9±1.3 ng/ml versus 5.8±1.1 ng/ml, p=0.011; CGRP: 5.5±2.3 ng/ml versus 7.3±2.7 ng/ml; p=0.002; VIP: 4±0.9 ng/ml versus 5.1±1.5 ng/ml, p=0.007). No significant changes were observed in the control eyes of allergic patients challenged with diluent and in healthy subjects after allergen provocation.


CONCLUSIONS
Locally-released neuromediators may participate in modulating the allergic response of the ocular surface.
Department of Ophthalmology, University of Rome Campus Bio-Medico, Rome, Italy.
Marta
M
Sacchetti
Alessandra
A
Micera
Alessandro
A
Lambiase
Stefania
S
Speranza
Flavio
F
Mantelli
Girolamo
G
Petrachi
Sergio
S
Bonini
Stefano
S
Bonini
D000328:Adult; D000485:Allergens / Q000737:chemistry*; D000818:Animals; D001985:Bronchial Provocation Tests / Q000379:methods; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D003233:Conjunctivitis, Allergic / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005123:Eye / Q000276:immunology; D005260:Female; D006801:Humans; D007249:Inflammation; D008297:Male; D009478:Neuropeptide Y / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry*; D039981:Pyroglyphidae / Q000378:metabolism; D013666:Tears / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000737:chemistry
D000485:Allergens; D009478:Neuropeptide Y; D009479:Neuropeptides; D014660:Vasoactive Intestinal Peptide; D015740:Calcitonin Gene-Related Peptide
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