Activation of mouse protease‐activated receptor‐2 induces lymphocyte adhesion and generation of reactive oxygen species

Background and Purpose: Protease‐activated receptor‐2 (PAR‐2) is expressed on lymphocytes and endothelial cells, and plays a significant role in inflammatory reactions. Since leukocyte‐endothelial cell interaction and reactive oxygen species (ROS) generation are hallmarks of the development of inflammation, the effects of PAR‐2 activation by trypsin on lymphocyte adhesion and ROS generation was examined utilising PAR‐2 wild type and knockout (PAR‐2−/−) mice. Experimental Approach: Lymphocyte adhesion to the luminal surface of mouse isolated aortae was measured using 51 Cr‐labelled leukocytes and ROS generation from isolated lymphocytes was quantified using chemiluminescence. Key results: Trypsin induced adhesion of lymphocytes when added exogenously to the endothelial surface of the aorta for 30 min. Similarly, increased lymphocyte adhesion was also observed when mice were injected with trypsin intravenously 24 h prior to the adhesion assay, an effect which was partly ICAM‐1 mediated. Trypsin also increased ROS generation from isolated mouse lymphocytes in a dose‐dependent manner. The increase in lymphocyte adhesion and ROS production in response to trypsin were abolished in PAR‐2−/− mice indicating a PAR‐2 dependent mechanism. Superoxide dismutase had a greater inhibitory effect in PAR‐2−/− mice compared to wild type mice when lymphocytes were stimulated with PMA but not trypsin. Conclusions and Implications: The present study indicates that activation of PAR‐2 may be an important factor in modulating lymphocyte adhesion and ROS generation. The results have implications for developing anti‐inflammatory strategies. British Journal of Pharmacology (2006) 149 , 591–599. doi: 10.1038/sj.bjp.0706905