Respiratory Difficulties in Mice Treated with Lysenin, a Protein Purified from the Coelomic Fluid of the Earthworm Eisenia foetida

Lysenin is a 33-kDa protein isolated from the coelomic fluid (CF) of the earthworm Eisenia foetida. Purified lysenin binds specifically with sphingomyelin (SM) in the cell membrane. Lysenin (at doses above 120 μg/kg) is lethal to mice when injected intravenously. Mice experience respiratory problems, gasping violently, and dying within a few minutes after the injection. Examining the effects of lysenin histologically, we often found ghosts of erythrocytes and aggregates of disintegrated platelets in the alveolar capillaries. These aggregates might have blocked the bronchial blood circulations. Lysenin caused no apparent histological change to other cells such as type I and type II alveolar epithelial cells and endothelial cells of the alveolar capillaries. The death of mice injected with lysenin might have been due to respiratory difficulty caused by thrombi formation and hemolysis induced by the binding of lysenin with SM in the plasma membranes of platelets and erythrocytes, respectively.