ATP-induced mucin release from cultured airway goblet cell involves, in part, activation of phospholipase A2

Adenosine triphosphate (ATP) has been shown to stimulate mucin release by activation of protein kinase C (PKC) following activation of phospholipase C (PLC) coupled to the P(2) receptor via G-proteins. The aim of the present study was to investigate pathways downstream to the PKC activation in ATP-induced mucin release from primary hamster tracheal surface epithelial (HTSE) cells. The release of mucin was determined by chromatographic procedure after metabolic labeling of mucin with [(3)H]-glucosamine. The results were: i) ATP induced the release of arachidonic acid, which caused the release of mucin . Pretreatment with mepacrine (0.3 mM), a phospholipase A(2) (PLA(2)) inhibitor, inhibited the ATP-induced arachidonic acid and mucin release. Oleoyloxyethylphosphocholine, another PLA(2) inhibitor, gave similar results. ii) An activator of PKC, 4 beta -phorbol-12 alpha -myristate-13-acetate (PMA, 1 muM) induced mucin release, which was inhibited by mepacrine pretreatment. iii) Downregulation of PKC by prolonged (16 h) PMA treatment caused inhibition of ATP-induced mucin release. Treatment of PKC downregulated HTSE cells with mepacrine did not further decrease the ATP-induced mucin release. These results suggest that PLA(2) is involved in ATP-induced mucin release and its activation is sequential to the PLC-PKC pathway. (C) 2001 Prous Science. All rights reserved.