Hemorrhagic shock-induced changes in the cathepsin D activity in the intestinal wall and blood serum in rats

Hemorrhagic shock causes release of lysosomal proteolytic enzymes which contribute to intestinal wall destruction and can be moved into the circulation as well as into the gut lumen. The aim of the study was to examine the activity of cathepsin D in relation to the intestinal wall injury after 60 minutes of untreated hemorrhagic shock in rats. The total cathepsin D activity was investigated in duodenum, jejunum, ileum, cecum and colon, as well as in systemic and mesenteric blood serum, and the biochemical results were compared with morphological changes in the respective segments including immunohistochemical expression of cathepsin D. We found an increase in cathepsin D activity in duodenum and significant decrease in other parts of the gut in shocked rats. The enzyme activity increased also in blood serum, especially systemic (p < 0.05) and insignificantly in mesenteric blood. However, sham-operated animals (one-side carotid artery occlusion) revealed a significant increase in cathepsin D activity measured in mesenteric blood. The shock resulted in lowering protein concentration in the intestinal wall and its increase in mesenteric blood. The contents of peptides and amino nitrogen, as potential proteolytic reaction products, changed in different ways in various segments of intestine. Morphologically, the most intensive destruction was observed in ileum, duodenum and jejunum. Lifting of epithelial layer from lamina propria was the most frequently observed lesion of the intestinal wall after 60 minutes of shock. More advanced lesions, such as denuded mucosa with disintegration of lamina propria, occurred rarely and were not observed in colon and rectum. By means of polyclonal antibodies against cathepsin D, we found that the strong expression of this enzyme was in epithelial layer--the part of intestinal wall which was partially detached into gut lumen due to hemorrhagic shock. The changes of cathepsin D activity after 60 minutes of hemorrhagic shock were correlated with signs of morphological damage to the intestinal wall. Cathepsin D liberation in the intestinal wall during shock indicates the lysosomal membranes impairment and can confirm involvement of proteases in the damage to the intestinal tissue. We conclude that liberation of intestinal cathepsin D is an early phenomenon during hemorrhagic shock which may contribute to the local wall disintegration and activation of systemic inflammatory response.