Lysozyme, a mediator of sepsis that deposits in the systemic vasculature and kidney as a possible mechanism of acute organ dysfunction.

In septic shock (SS), dysfunction of many organ systems develops during the course of the illness, although the mechanisms are not clear. In earlier studies, we reported that lysozyme-c (Lzm-S), a protein that is released from leukocytes and macrophages, was a mediator of the myocardial depression and vasodilation that develop in a canine model of Pseudomonas aeruginosa SS. Whereas both of these effects of Lzm-S are dependent on its ability to intrinsically generate hydrogen peroxide, we subsequently showed that Lzm-S can also deposit within the vascular smooth muscle layer of the systemic arteries in this model. In the present study, we extend our previous findings. We used a canine carotid artery organ bath preparation to study the time course and dose dependence of Lzm-S deposition within the vascular smooth muscle layer. We used a human aortic vascular smooth muscle cell preparation to determine whether Lzm-S can persistently inhibit contraction in this preparation. We also used a canine P. aeruginosa model to determine whether Lzm-S deposition might occur in other organs such as the kidney, liver, and small intestine. The results showed that, in the carotid artery organ bath preparation, Lzm-S deposition occurred within minutes of instillation and there was a dose-response effect. In the human aortic vascular smooth muscle cell preparation, Lzm-S inhibited contraction during a 4-day period. In the in vivo model, Lzm-S accumulated in the kidney and the superior mesenteric artery. In a canine renal epithelial preparation, we further showed that Lzm-S can be taken up by the renal tubules to activate inflammatory pathways. We conclude that Lzm-S can deposit in the systemic vasculature and kidneys in SS, where this deposition could lead to acute organ dysfunction.