DIFFERENTIAL EXPRESSION OF ANNEXIN-I AND ANNEXIN-II IN BOVINE BRONCHIAL EPITHELIAL-CELLS

Annexins I and II have been proposed to participate in regulation of i nflammation and cell proliferation. In the present study, we examined the expression of annexins I and II in various levels of the bovine re spiratory tract and in cultured bovine bronchial epithelial cells. Imm unoblot analysis of whole-tissue extracts revealed low-level expressio n of annexins I and II in bronchial mucosa mainstem to fourth generati on. In contrast, high levels of annexins I and II (15- to 20-fold high er than in the bronchial mucosa) were seen in the distal lung parenchy ma. Immunohistochemical staining of tracheobronchial tissue sections w ith anti-annexin I antibody revealed an uneven positive reaction of ab out 30 to 40% of the columnar differentiated ciliated and secretory ce lls, with no obvious positivity within the nondifferentiated basal epi thelial cell layer. In contrast, anti-annexin II antibody reacted near ly. uniformly within the basal cell layer, with no obvious decoration of the differentiated cell types. These results were confirmed by immu noblot analysis of annexin I and II: in density fractionated populatio ns of basal and secretory/ciliated epithelial cells. Both annexins I a nd II were expressed at constitutive levels in bovine bronchial epithe lial cells grown in glucocorticoid- and serum-free medium, and dexamet hasone increased expression of both proteins in a concentration-depend ent manner. We conclude that annexins I and II are differentially expr essed in the differentiated ciliated cells and undifferentiated basal cells. We suggest that differential expression of annexins I and II in the airway may play a role in tissue injury and repair.