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Published on: September 9, 2014
Paraoxonase 1 (PON1) inhibits monocyte-to-macrophage differentiation
Mira Rosenblat1, Nina Volkova, John Ward
1The Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Rambam Medical Center, Haifa, Israel.
Objective:
To analyze paraoxonase 1 (PON1) effect on monocyte-to-macrophage differentiation.
Methods And Results:
THP-1 monocytic cell-line and mouse peritoneal macrophages (MPM) were studied. Markers for monocytes differentiation included: morphological changes, CD11b and CD36 expression, and cellular oxidative stress. PON1KO MPM were more differentiated than control C57BL/6 MPM. Intraperitoneal injection of recombinant PON1 (rePON1) to C57BL/6 or to PON1KO mice significantly increased serum, MPM, and tissues PON1 activities. These effects were associated with a significant decrease in CD11b in C57BL/6 and PON1KO MPM (by 21% and 35%, respectively), in CD36 (by 35% and 38%, respectively), and in cellular total peroxides content (by 18% and 20%, respectively). rePON1 also significantly inhibited CD11b and CD36 expression, and cellular total peroxides during PMA-induced THP-1 monocytes differentiation, by 68%, 56% and 53%, respectively. Similar effects were observed upon using reconstituted HDL (rHDL) +rePON1, or human HDL +rePON1, in comparison to rHDL or to human HDL, as well as, HDL from C57BL/6 vs. PON1KO mice. Inhibition of monocyte-to-macrophage differentiation was demonstrated also by several dietary antioxidants such as vitamin E, gallic acid, or punicalagin (the major polyphenol in pomegranate). Whereas NADPH oxidase was not involved in PON1 anti-differentiation effect, mitochondrial complex I could be involved, as rotenone (complex I inhibitor) significantly decreased (by 77%) the expression of CD11b during THP-1 differentiation. Finally, blocking PON1 sulfhydryl group with N-ethylmalemide significantly attenuated PON1 inhibitory effect on THP-I monocyte-to-macrophage differentiation.
Conclusion:
HDL-associated PON1 inhibits monocyte-to-macrophage differentiation, and this effect could be related to PON1 peroxidase-like activity which involves its free sulfhydryl group.
Insights
Paraoxonase 1 (PON1) inhibits monocyte differentiation into macrophages. This effect, linked to PON1
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Monocyte-to-macrophage differentiation is a key process in inflammatory responses.
- Paraoxonase 1 (PON1) is an enzyme associated with high-density lipoprotein (HDL) and known for its antioxidant properties.
Purpose of the Study:
- To investigate the role of PON1 in regulating monocyte-to-macrophage differentiation.
- To explore the mechanisms underlying PON1's influence on this cellular process.
Main Methods:
- Utilized THP-1 monocytic cell line and mouse peritoneal macrophages (MPM).
- Assessed differentiation markers including morphology, CD11b/CD36 expression, and cellular oxidative stress.
- Administered recombinant PON1 (rePON1) and HDL-bound PON1 in vivo and in vitro.
- Investigated the involvement of NADPH oxidase and mitochondrial complex I, and the role of PON1's sulfhydryl group.
Main Results:
- PON1 knockout (PON1KO) macrophages showed enhanced differentiation compared to controls.
- rePON1 administration reduced differentiation markers (CD11b, CD36) and oxidative stress in both wild-type and PON1KO mice.
- rePON1 significantly inhibited differentiation markers and oxidative stress in PMA-induced THP-1 cells.
- HDL-associated PON1 demonstrated inhibitory effects on differentiation.
- Mitochondrial complex I, but not NADPH oxidase, appeared involved; PON1's sulfhydryl group was crucial for its inhibitory activity.
Conclusions:
- HDL-associated PON1 effectively inhibits monocyte-to-macrophage differentiation.
- This inhibitory effect is likely mediated by PON1's peroxidase-like activity, which depends on its free sulfhydryl group.
