The role of aminopeptidases in inflammatory and neoplastic tissues

Abstract

The role of leucine andalanine aminopeptidases is stidued in three different biologic systems: experimental wound healing in the rat, experimental carrageenan induced intraderman granulomas in the rat, and human laryngeal carcinomas. The wound healing experiments indicate that the proliferating granulation tissue has high quantities of aminopeptidases activity which is residing primarily intracellularly in granulocytes, macrophages, mast cells fibroblasts, and new budding vessels. The quantititave levels of tissue aminopeptidases correlate positively with the degree of cellularity of the wound and fibroblastic activity. Some aminopeptidases (isoenzymes) are secreted or released by the fibroblasts in be blood serum. Starch gel electrophoretic analysis demonstrates thses with different concentrations and migration rates. Two are probably released or secreted into the serum, and th third is membranous bound in the cytoplasm (lysosomal). The carrageenan intradermal granuloma demonstrates a different inflammatory reaction which is rich in macrophages and produces a different pattern of aminopeptidases activity. Macrophages produce a high tissue level of aminopeptidase activity which is intracellular bound and not readily leached out into the serum. Gel electrophoresis studies of aminopeptidases produced by the granuloma demonstrate that the tissue bound enzyme is the main component. In addition, there appears to be a mechanism, which is not understood, for specific induction or activation of lysosomal proteolytic and carbohydrase enzymes. This mechanism is dependent on the nature of composition of the injuring agent. Laryngeal carcinomas demonstrate high tissue homogenate levels and normal serum levels of aminopeptidase activities. These enzymes are located in the tumor stroma. They are not directly related to tumor invasiveness but to the degree of stromal proliferation. The tumor stroma behaves as though it were a non-healing wound constantly secreted proteolytic enzymes (aminopeptidases). A major problem that needs to be resolved is to find the operating mechanism by which malignant cells interact with their constantly proliferating fibroblastic stroma.