Possible role of calmodulin in the control of lysosomal enzyme release from human polymorphonuclear leukocytes

Human polymorphonuclear leukocytes (PMNs) were found to contain a mean +/- S.E.M. of 21.7 +/- 7.9 ng of immunoreactive calmodulin (CaM)/10(6) PMNs, which represents 0.032 +/- 0.001% of the total cellular protein. The functional role of CaM in the control of lysosomal enzyme release from human PMNs was investigated using several CaM antagonists. Trifluoperazine (TFP) (10(-6)-2 X 10(-5) M), pimozide (10(-6)-1.5 X 10(-5) M), chlorpromazine (CPZ) (10(-5)-10(-4) M) and promethazine (2 X 10(-5)-10(-4) M) inhibited in vitro lysosomal enzyme release from human PMNs induced by immunological (serum-treated zymosan, concanavalin A and formyl-L-methionyl-L-leucyl-L-phenylalanine) and nonimmunological (Ca++ ionophore A23187) stimuli. Trifluoperazine sulfoxide (TFP-S) and chlorpromazine sulfoxide (CPZ-S), which have very low affinity for CaM, had practically no inhibitory effect on lysosomal enzyme release. The inhibitory effect of TFP could be made irreversible by irradiating the cells with UV light. A sulfonamide derivative, W-7, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (10(-5)-2 X 10(-4) M), which selectively binds to CaM, inhibited the release of lysosomal enzymes from PMNs. In contrast, the chloride-deficient analog, W-5, N-(6-aminohexyl)-1-naphthalenesulfonamide hydrochloride, which interacts only weakly with CaM, had practically no inhibiting effect. The IC50 for enzyme release by a series of eight CaM antagonists was closely correlated (r = 0.89; P less than .001) with their affinity for binding to CaM, supporting the concept that these agents act by binding to CaM and thereby inhibiting lysosomal enzyme release.(ABSTRACT TRUNCATED AT 250 WORDS)