Kurzfassung

Pseudomonas aeruginosa (Pa) is a gram-negative bacteria that causes serious infections in immunocompromised, ill and injured individuals. These infections can lead to lengthy hospital stays, disabilities such as limb amputations and often death. Pa infections are difficult to treat because they resist the patient’s own immune defenses and often acquire resistance to antibiotics. Thus, researchers are looking for novel approaches to combat antibiotic resistant strains of Pa. It has recently...Pseudomonas aeruginosa (Pa) is a gram-negative bacteria that causes serious infections in immunocompromised, ill and injured individuals. These infections can lead to lengthy hospital stays, disabilities such as limb amputations and often death. Pa infections are difficult to treat because they resist the patient’s own immune defenses and often acquire resistance to antibiotics. Thus, researchers are looking for novel approaches to combat antibiotic resistant strains of Pa. It has recently been discovered that Pa produces a signaling molecule called 3OC12 which helps the bacteria produce virulence factors which protect it from the host’s immune defenses. Genetic mutant strains of Pa that can’t make or respond to 3OC12 have been shown to be much less virulent and more easily cleared in many animal models of Pa infection. This demonstrates the importance of 3OC12 production by Pa for the survival of the bacteria in the host.

Recently an enzyme called paraoxonase 2 (PON2), which is located in almost all cell types and organs, was found to rapidly inactivate 3OC12. This has led investigators to suggest that PON2 may be a component of the host’s defense which protects against Pa infection by inactivating 3OC12. However, in experimental cultured cell lines, 3OC12 itself was found to block (or "turn off") the ability of PON2 to inactivate 3OC12 by modifying the enzyme. This suggests that Pa might utilize 3OC12 to block PON2, circumventing potential protection afforded by PON2 during infection. Thus, if an individual’s PON2 levels and/or activity could be maintained or increased during infection, this could significantly protect the individual from antibiotic resistant Pa infections. Our long term goals are to a) definitively demonstrate that PON2 has the potential to protect from Pa infections and b) develop drugs which can sustain or enhance PON2 activities and/or levels in Pa infected individuals. Before these objectives can be met, however, a detailed understand of the mechanisms and cellular signaling pathways the mediate 3OC12’s ability to block PON2’s activity must first be identified. Therefore, in this study, we propose three specific aims. Under aim 1, the identification of the modifications to PON2, which are mediated by 3OC12, that result in the blocking of PON2 activity (inactivation) will be identified. Also, the cellular signaling circuits and proteins, that are initiated by 3OC12, which result in the modification of PON2 which blocks its activity, will be identified. These experiments are needed to identify therapeutic drug targets which can enhance PON2 activity. In aim 2, the sensitivity of PON2 to become inactivated (i.e. activity blocked) by 3OC12 in primary human cultured cells and in mouse lungs in live animals will be determined. These experiments will help predicte the efficiency of 3OC12, produced by Pa during infection, to inactivate PON2 in humans. In aim 3 the feasibility of using pharmacological agents to protect PON2 from becoming inactivated by 3OC12 will be tested in live mice. This will help establish the feasibility of using drugs in humans to enhance the individuals PON2 activity. Once these aims are successfully completed, future studies can be initiated to test and develop the experimental pharmacological agents into drugs to limit Pa infections.

Infection with multi-drug resistant bacteria, such a Pa, is a major and growing complication of immunocompromised individuals such as those with burn wounds, HIV infection, cystic fibrosis and those undergoing chemotherapy. It is also is a major complication of combat-related injuries in US service members. Such infections can result in death, limb amputations and extended periods of disability. A therapy that enhances the host’s ability to disrupt Pa, such as increasing PON2 levels/activity as proposed in this study, could be used alone, or together with antibiotics, greatly extending the availability of effective treatment options for infected service members. Because PON2 is expressed in nearly all cell types and tissues, this strategy would be expected to be applicable to any tissue colonized by Pa. This is an important consideration given the diverse location of combat-related injuries.» weiterlesen» einklappen