Acidic mammalian chitinase (AMCase): A new target for ocular diseases

Chitin, the second most abundant polysaccharide in nature, is not expressed in mammalian systems, but is found in the structural coatings of fungi, the exoskeleton of many arthropods and parasitic nematodes. The host defense against chitin-containing pathogens includes the production of chitinases. An acidic mammalian chitinase (AMCase) is produced by human epithelial cells of the lower airways and conjunctiva via a Th2-specific, IL-13-dependent pathway, and appears to be associated with asthma and inflammatory ocular pathologies. Animal studies showed that AMCase activity was increased in tears of rabbits with endotoxin-induced uveitis, and that this activity was attenuated and inhibited by chitinase inhibitors. The level of AMCase activity was found to be elevated in the tears of patients with vernal keratoconjunctivitis and seasonal allergic conjunctivitis, and specific mRNA, extracted by conjunctival epithelial cells, correlated with AMCase activity. An increase in AMCase activity was found in the tears of patients affected by dry eye syndrome, which correlated with specific mRNA. Therefore, it appears that AMCase represents an important mediator in the pathogenesis of Th2-driven inflammatory ocular diseases. Copyright © 2011 Prous Science, S.A.U. or its licensors. All rights reserved.