Mechanism of interaction between ocular and nasal neurogenic inflammation in allergic rhinoconjunctivitis

Purpose The mechanisms of naso-ocular interaction in allergic rhinoconjunctivitis are not well understood. Neurogenic inflammation affects both eyes and nose via the same neurogenic factors. The purpose of this study was to investigate the effects of neurogenic inflammation on conjunctival inflammation following nasal allergen provocation. Methods Sensitized rats were exposed to ovalbumin (OVA) via the nose. Parts of the nasal mucosa and conjunctivae were sliced and used for hematoxylin–eosin staining, immunohistochemical analysis, western blotting, and real-time polymerase chain reaction. The slides were observed under a light microscope, and the acquired images were analyzed. The levels of substance P (SP), vasoactive intestinal peptide (VIP), and nerve growth factor (NGF) were detected. Results The levels of SP, VIP, and NGF were increased in both nasal mucosa and conjunctivae 1 h and 24 h after OVA administration ( p < 0.05). Higher levels of SP, VIP, and NGF expression were observed in the nasal mucosa and conjunctivae 24 h after OVA administration ( p < 0.05). Following damage of the nasal sensory nerves by capsaicin, the protein and mRNA levels of SP, VIP, and NGF were reduced. Conclusion In conclusion, the increased levels of VIP, SP, and NGF might be responsible for the ocular reaction following nasal challenge with allergen in rats.