The mechanism for anthracycline-induced inhibition of collagen biosynthesis

One of the recognized side effects accompanying anti-neoplastic anthracycli nes administration is poor wound healing resulting from impairment of colla gen biosynthesis. However, the precise mechanism of anthracyclines-induced inhibition of collagen synthesis has not been established. We have suggeste d that prolidase, an enzyme involved in collagen metabolism, may be one of the targets for anthracyclines-induced inhibition of synthesis of this prot ein. Prolidase [EC 3.4.13.9] cleaves imidodipeptides containing C-terminal proline, providing large amount of proline for collagen synthesis, Therefor e, we compared the effect of daunorubicin and doxorubicin on prolidase acti vity and collagen biosynthesis in confluent cultured human skin fibroblasts . We have found that daunorubicin and doxorubicin coordinately induced the inhibition of prolidase activity (IC50 = 0.3 and 10 muM, respectively) and collagen biosynthesis (IC50 = 1 and 15 muM, respectively) in cultured human skin fibroblasts. The inhibitory effect of daunorubicin or doxorubicin on prolidase activity and collagen biosynthesis was not due to anti-proliferat ive activity of these drugs as shown by cell viability tetrazoline test. Th e decrease in prolidase activity due to the treatment of confluent cells wi th the anthracyclines was not accompanied by any difference in the amount o f enzyme protein recovered from these cells as shown by Western immunoblot analysis. It may be suggested that the inhibition is a post-translational e vent. Since prolidase is metalloprotease, requiring manganese for catalytic activity, and anthracyclines are known as chelators of divalent cations, w e considered that the chelating ability of anthracyclines might be an under lying mechanism for the anthracyclines-induced inhibition of prolidase acti vity. In order to determine the ability of daunorubicin or doxorubicin to f orm complexes with manganese (II), potentiometric method was employed based on the measurement of protonation constant by pH-metric titrated assay. We have found that both anthracyclines form stable complexes with manganese ( II). The composition of the daunorubicin-Mn(II) complex was calculated as 3 : 1 while that of doxorubicin-Mn(II) complex was 2:1. The constant stabilit y value for the investigated complexes were calculated as beta (av) = (1.74 +/- 0.01) x 10(23) for daunorubicin, and beta (av) =(1.99 +/- 0.025) x 10( 11) for doxorubicin. The higher ability of daunorubicin vs, doxorubicin to chelate manganese and inhibit prolidase activity may explain the potential mechanism for its greater potency to inhibit collagen biosynthesis. (C) 200 1 Elsevier Science B.V. All rights reserved.