Catalytically inactive cyclooxygenase 2 (COX-2) and absence of PGE2 biosynthesis in murine peritoneal macrophages following in vivo phagocytosis of heat-killed Mycobacterium bovis BCG (52.17)

Abstract

Abstract The conclusion that peritoneal macrophages (MØ) isolated from mice given heat-killed BCG (HK-BCG) intraperitoneally do not release PGE2 ex vivo has been established for over 25 years. However, when peritoneal MØ from untreated mice are treated in vitro with HK-BCG, MØ express COX-2, a rate-limiting enzyme for PGE2 biosynthesis, with increased PGE2 release. The present study of C57BL/6 mouse peritoneal MØ treated in vitro or in vivo with HK-BCG was undertaken to determine whether COX-2 is expressed and whether PGE2 release is dependent on its catalytic activity. The results indicate that MØ treated with HK-BCG in vivo expressed COX-2 that was catalytically inactive and localized subcellularly in the cytoplasm but not associated with the nuclear envelope (NE). In contrast, MØ treated in vitro expressed catalytically active COX-2 that was localized in the NE and diffusely in the cytoplasm. In addition, COX-1, constitutively localized in the NE and ER in untreated M , was dissociated from the NE in response to in vivo but not in vitro HK-BCG treatments. These results indicate that COX-1 and COX-2 dissociated from the NE are catalytically inactive, which accounts for the lack of PGE2 production by local MØ activated in vivo with HK-BCG. Our studies suggest that following phagocytosis of intracellular bacteria, local MØ express catalytically inactive COX-2, which may enhance M -mediated innate and Th1 acquired immune responses against intracellular infections sensitive to endogenous PGE2. (NIH RO1 HL71711, DOD DAMD 17-03-1-0004)