The myeloid leukemia cell line HL-60 produces a factor that induces chloride secretion in cultured epithelial cells

When activated, polymorphonuclear leukocytes (PMNs) produce a small soluble factor, termed neutrophil-derived secretagogue (NDS), that elicits electrogenic Cl- secretion--the transport event responsible for hydration of mucosal surfaces. Work toward purification of this factor has been hampered by variability in activity of PMN-derived NDS. Using a human-derived intestinal epithelial cell line (T84) that serves as a model for studies of the regulation of electrogenic Cl- secretion, we find that the human promyelocytic leukemia cell line HL-60 secrets a factor with NDS-like activity. Buffer conditioned by HL-60 cells (10(7) cells/ml for 1 h), when applied to T84 monolayers grown on permeable supports and analyzed by routine electrophysiological techniques, elicited a short-circuit current (Isc) of 11.7 +/- 1.02 microA/cm2. This short-circuit current was sensitive to bumetanide, an inhibitor of the basolateral Na-K-2Cl cotransporter, and was dependent on the presence of chloride in the assay buffers. Such data indicate that buffer conditioned by HL-60 cells stimulates electrogenic Cl- secretion. Like NDS, the active factor in HL-60-conditioned buffer has a nominal molecular weight of less than 500 and was increased by activation of cells with phorbol ester. 125I and 86Rb efflux assays confirmed that the secretagogue released by stimulated HL-60 cells, similar to PMN-derived NDS, preferentially stimulates opening of Cl- rather than K+ channels in T84 cells. Lastly, release of NDS-like bioactivity increases when HL-60 cells are differentiated toward granulocytes compared to cells differentiated toward monocytes.