Investigation into the role of annexin 1 in the microcirculation of annexin 1 knockout mice

Abstract

Glucocorticoids are used therapeutically for their anti-inflammatory and immunosuppressive actions. One of the ways they produce their potent effects is via regulation of the anti-inflammatory protein Annexin I (ANX-AI; 37 kDa protein). Whereas there is sufficient information on the pharmacological properties of ANX-Al and its bioactive peptides, as they have been studied in several models of experimental inflammation, much less is known about the functions of the endogenousp rotein. In this thesis I have had accesst o the recently generatedA NX-Al knockout (ANX-AI'4-) mice with the scope of elucidating the role of the endogenous mediator on the process of leukocyte (mainly neutrophil) recruitment. Two main models were used to assess leukocyte recruitment: a) a flow cytometry protocol was implemented to quantify the extent and the nature of the cellular influx into the inflamed peritoneal cavity and b) intravital microscopy of the inflamed cremaster muscle was used to identify which step of leukocyte recruitment was potentially altered. Overall, ANX-A14- mice were found to have a heightened sensitivity to inflammation. In the peritonitis model, ANX-AI4- mice displayed a higher degree of neutrophil recruitment into the peritoneal cavity, however this occurred in a stimulus specific manner. The functional role of the protein in this model was confirmed by using transgenic mice that over-express ANX-Al. These mice were shown to have the opposite response to the ANX-A14- mice, since they had a reduced influx of neutrophils into the peritoneal cavity in response to zymosan. Intravital microscopy studies i pinpointed the emigration phase of leukocyte recruitment to be significantly altered in ANX-AI-1- mice, and this defect was seen with application of different inflammatory agents. In conclusion, this thesis has demonstrated, for the first time, that there are altered leukocyte-endothelium interactions in ANX-Al-- mice, and these results indicate a pivotal role for endogenous ANX-Al in the process of neutrophil recruitment that is fundamental to the host inflammatory response.