In a previous study, we found that crocidolite (an asbestos fiber) had an inhibitory effect on the differentiation process of HL-60 cells induced by dimethyl sulfoxide (DMSO). Here we describe the cathepsin B-like enzyme in HL-60 cells and the changes of its activity during cell differentiation with or without crocidolite treatment. The cathepsin B-like enzyme in HL-60 cell extracts had almost the same characteristics as the already known cathepsin B as for the pH optima and the effects of proteinase inhibitors. The cathepsin B-like enzyme activity increased according to the cell differentiation induced by DMSO, however, its activity was depressed by crocidolite treatment.
On the basis of these results, it is shown that depression of the HL-60 cell differentiation by crocidolite is correlated with the decrease of cathepsin B-like enzyme activity.
