Differential Expression Of Granzyme B In Macrophages
Matthew R. Zeglinski, Christopher T. Turner, David J. Granville.
University of British Columbia, Vancouver, BC, Canada.
Background: Granzyme B (GzmB) is a serine protease widely recognized for its intracellular apoptotic role and its extracellular role in matrix remodeling. Although GzmB is most commonly associated with cytotoxic T-lymphocytes, other immune cells, including macrophages, express GzmB. Although macrophage expression of GzmB has been reported, it is unknown what subtype(s) of macrophages express GzmB and whether GzmB is retained within the cell or secreted into the extracellular environment. Therefore, we set out to determine the expression profile and spatial distribution of GzmB in differentially polarized macrophages. Methods: THP-1 monocytes were differentiated and polarized into M0, M1, M2a, and M2c subtypes. Gene expression was determined by qPCR. GzmB concentrations in cell lysates and culture supernatants was determined by ELISA. Cellular localization of GzmB was determined by confocal microscopy.Results: GzmB was expressed by all subtypes as determined by qPCR and ELISA. M2a macrophages expressed 6-fold more GzmB mRNA compared to M1 and M0 subtypes. M0 and M1 subtypes retained GzmB whereas M2a and M2c subtypes secreted the majority of GzmB. Confocal imaging demonstrated peri-nuclear GzmB staining in M0 and M1 subtypes, whereas GzmB was widely distributed in M2a cells. SerpinB9 was expressed by all subtypes with the highest levels observed in M1 cells. Perforin (Pfn) was also expressed by all subtypes with M2a cells expressing 4-fold more Pfn mRNA compared to M0 and M1 subtypes. Conclusion: Secretion of GzmB by M2a cells may contribute to matrix remodeling in chronic inflammatory disease.
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