Effects of Gedunin on THP-1 Macrophages Polarization

Inflammation is a protective response from the organism against internal or external stimuli(1). Dysfunctions in the resolution of inflammation can lead to chronic diseases, such as rheumatoid arthritis, neurodegenerative diseases, and cancer(2). Macrophages are key innate immune cells in this process. They can acquire a classic pro-inflammatory (M1) phenotype, secreting pro-inflammatory cytokines, or an alternative anti-inflammatory (M2) phenotype, suppressing inflammation and inducing tissue regeneration(3). Heat shock protein (HSP)90 is a molecular chaperone that helps in the folding and activity of some proteins, including cytokines(4). Its inhibition can reduce the inflammatory response and increase the levels of some pro-resolutive molecules(4,5). Gedunin is a natural limonoid, known for its anti-inflammatory and (HSP)90 inhibitory activities(4). This work aims to study the effects of gedunin in M1 macrophages, using the THP-1 cell line, and its role in macrophage polarization to M2. THP-1 cells were differentiated in 24- or 96-well plates using PMA (20ng/mL), and polarized to the M1 phenotype with LPS (100ng/mL) and IFN-γ (20ng/mL), or to the M2 phenotype with IL-4 (20ng/mL) and IL-13 (20ng/mL), or not polarized (M0). After 24 h stimuli, M0 and M1 macrophages were treated with gedunin (5, 10, or 25µM) or dexamethasone (1µM) for 24 h. Cell viability was estimated by MTT; pSTAT-6, STAT-6, Arginase-1, COX-2, and 15-LO the levels were measured by Western blot, and TGF-β1, IL-10, and IL-6 by ELISA. Gedunin treatment was not toxic to M0 or M1 cells. The anti-inflammatory potential of gedunin was confirmed by reduced COX-2 levels in M1-treated cells. Gedunin-treated cells presented elevated levels of IL-10, TGF-β1, and IL-6 when compared with the other groups. These preliminary results elucidate a potential pro-resolutive role of gedunin.
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