Purpose: Chitin is abundant in the structural coatings of fungi, insects, and parasitic nematodes. The host defense against chitin-containing pathogens includes production of chitinases. An acidic mammalian chitinase (AMCase) is produced in human epithelial cells of lower airways through a TH2-specific, interleukin-13-dependent pathway and appears to be associated with allergic asthma. The role of AMCase in allergic ocular pathologies has never been studied previously.
Methods: Six patients with vernal keratoconjunctivitis (VKC), 7 patients with season allergic conjunctivitis (SAC), and 8 healthy controls (4 children and 4 adults) were enrolled in this study. AMCase activity was measured in tears, RNA was extracted from epithelial cells of the conjunctiva, and AMCase mRNA expression was evaluated by real-time polymerase chain reaction.
Results: AMCase activity was increased in patients affected by VKC (33.7 +/- 10.8 nmol/mL/h) and SAC (7.3 +/- 4.1 nmol/mL/h) compared with healthy controls (1.6 +/- 0.2 nmol/mL/h), and AMCase activity was higher in subjects with VKC (P = 0.0001). Receiver operating characteristic analysis showed that the sensitivity and specificity were 100%, addressing the use of AMCase assay in the biochemical diagnosis of VKC and SAC. AMCase mRNA was detected in epithelial cells of the conjunctiva, and the expression was significantly higher in VKC and SAC.
Conclusions: AMCase may be an important mediator in the pathogenesis of TH2 inflammation eye diseases, suggesting a potential diagnostic and therapeutic target in these pathologies.