Background: Vimentin is one of the best-characterized type III intermediate filament (IF). The importance of this protein reflects the fact that it plays a pivotal role in the structure and function of the cells as well as is an important intermediate during pathological processes. Among its physiological and pathological role there are such an processes as: tissue repair and wound healing, monocyte to macrophage differentiation, angiogenesis, tumorigenesis, digestive diseases1,2. It was also shown that vimentin has direct influence on NLRP-3 activation and downstream events4. Also during the course of rheumatoid arthritis (RA), extracellular vimentin, citrullinated by peptidyl arginine deaminase (PAD) is one of the most important antigen against which anti-citrullinated antibodies are produced, enhancing chronic inflammation 3.
Objectives: In this work we have focused on regulation of vimentin expression in the course of phorbol myristate acetate (PMA) - induced monocyte to macrophage differentiation as well as calpain-1 and caspase-3 involvement in this process. PMA-differentiated macrophages are base for further induction of inflammasome, therefore it is important to investigate how different vimentin expression influence on inflammasome activation. Finally we also investigated the ability of PAD4 enzyme to vimentin citrullination and influence of this process for cleavage this IF by caspase-3 and calpain-1, which can has impact in the course of RA pathogenesis.
Results: THP-1 human monocyte cell line was subjected for various PMA concentrations and exposition time after which western blot analysis were performed using antibodies against vimentin, caspase-3, NLRP-3 and GSDMD. We have noticed some important changes of vimentin expression and it correspondence to changes in NLRP3 and GSDMD expression. We have also subjected recombinant vimentin to recombinant PAD4 citrullination and noticed difference in cleavage of citrullinated vimentin by calpain-1. Our studies also indicate that the products of vimentin cleavage may have different effects on LPS-primed macrophages than full-length vimentin.