The role of proteases in bacterial infection and burn injury.

摘要

Sepsis results from uncontrolled growth of bacteria in the body following a traumatic injury. A severe metabolic consequence of bacterial infection is an increase in whole body protein breakdown, particularly in the muscle mass of the body. The purposes of this project were to study the effects of 20S proteasome inhibitor, Z-Ile-Glu-Ala(OBut)Ala-Leucinal (4mg/kg) on increased muscle proteolysis due to burn injury followed by Pseudomonas aeruginosa infection and on the growth of Pseudomonas aeruginosa . A rat model that reflects characteristics of sepsis such as increased body temperature, muscle loss, and increased protein degradation was developed. The proteasome inhibitor was administered directly to animals with very few adverse effects for 24 and 72 h following burn-infection. The proteasome inhibitor did decrease the increase in proteolysis of skeletal muscles, but did not prevent the loss in muscle mass that followed burn-infection.; The effect of 5 different classes of protease inhibitors on Pseudomonas aeruginosa was studied. Of the inhibitors examined, only the proteasome inhibitors decreased the rate of bacterial growth. An enzyme activity that resembles the Escherichia coli HslUV protease was partially purified from Pseudomonas aeruginosa. This HslUV-Iike protease, was inhibited by Z-Ile-Glu-Ala(OBut)Ala-Leucinal, and therefore may be the intracellular target of the proteasome inhibitors. Clp P peptidase from Pseudomonas aeruginosa was isolated for the first time. This enzyme was not inhibited by proteasome inhibitors. The N-terminal sequence of the Clp P peptidase from Pseudomonas aeruginosa shows 80% homology to the Clp P peptidase, from Yersinia enterocolitica. Our studies indicate a future role for protease as targets of antimicrobial compounds.