Identification of the 37kda Annexin-A1 Protein in Tears of Normal Subjects and Association of its 33kda Inactive Form with Active Vernal Keratoconjunctivitis Patients

Abstract

Background: Annexin-A1 (Anx-A1) is a glucocorticoid-regulated 37kDa protein with powerful anti-inflammatory actions: enhanced release from target cells occurs following addition of the anti-allergic cromone drugs. Anx-A1 is inactivated by proteolytic cleavage of the N-terminus and increased amounts of the cleaved 33kDa product correlate with inflammatory responses. Aim: To investigate if Anx-A1 is detectable in human tear specimens from patients with vernal keratoconjunctivitis (VKC). Methods: Tear specimens were collected from patients affected by active VKC (n=23) before and after therapy with Alomide (equivalent to Lodoxamide) 0.1%(n=11) for 10 daysand non-inflammatory control tear specimens from healthy volunteers (n=17) who gave informed consent. Anx-A1 protein levels were measured by ELISA and by Western blotting. Results: In cell-free tear specimens from healthy donors, the concentration of Anx-A1 was 433.6 ± 54.3 pg/ ml (n=17) and >90% was in the intact form. In tears from VKC patients however, total Anx-A1 increased to 1908 ± 319.3pg/ml (n=23; p 80% is intact form, n=11, p<0.01). Conclusion: Anx-A1 is constitutively present in normal human tears and is proteolytically cleaved to inactivation during chronic allergic disease. Alomide treatment decreased the proportion of cleaved protein in VKC patients, and this is perhaps related to its therapeutic action.