Effects of Polymorphonuclear Neutrophils on Protein Synthesis by Alkali-Injured Rabbit Corneas: A Preliminary Study

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Abstract

Invasion of polymorphonuclear neutrophils (PMN) into injured cornea is one of the early events in corneal wound-healing. In the present studies, we examine the mutual effects on protein synthesis by PMN and injured and normal corneas when they are cocultured. PMN were labeled with [35S]methionine in the presence or absence of normal or alkali-injured rabbit corneas for 1-5 h. The acid-insoluble 35S-labeled proteins in medium, cells, and tissues were measured. Our data indicate that alkaliinjured rabbit corneas induce higher rates of incorporation of [35S]methionine and secretion of 35S-labeled newly synthesized proteins by PMN. The newly synthesized 35S-labeled proteins were then analyzed by twodimensional PAGE. The results indicate that alkaliinjured and normal rabbit corneas enhance the synthesis and secretion of a 18-kD protein by PMN. In contrast, alkali injury greatly reduced the secretion of a group of proteins having molecular weights of ~30 kD by rabbit corneas. The alkali-injured corneas synthesize a new 200- kD protein (AC-200) in tissues and increase the secretion of a 120-kD protein (AC-120) into the culture medium. Furthermore, PMN slightly inhibits the incorporation of [35S]methionine and alter the synthesis of several 35S-labeled proteins by normal and injured corneas. For example, incubation with PMN abolishes the synthesis of the AC-200 protein, but enhances the secretion of the AC-120 protein by the alkali-injured corneas. However, the function and nature of these proteins remain largely unknown. Further studies are needed to elucidate the biological roles of these polypeptides during corneal wound healing.

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