The effect of soluble Dexamethasone on pro-inflammatory macrophages
“Multiple Sclerosis (MS) is a chronic autoimmune disorder in which inflammation in the central nervous system damages neural conduction, resulting in MS signs and symptoms. Macrophages are immune cells that contribute to inflammation. In vivo, macrophages can take up a spectrum of phenotypes. In the laboratory, we can model extreme inflammatory (M1) and pro-regenerative (M2) phenotypes in vitro. M1 macrophages secrete cytokines and reactive oxygen species that damage myelin and regulating their phenotype may be therapeutic in MS.
Dexamethasone (DXM) is a steroid that inhibits inflammatory gene expression in macrophages. However, this drug targets and reacts with additional cells in our body as well, contributing to harmful side effects. Therefore, minimizing the amount of DXM needed for treatment would be beneficial to patients. We hypothesize that we can achieve anti-inflammatory effects and reduce toxicity by using Acetalated-Dextran (AceDEX) microparticles loaded with DXM that transport DXM into macrophages.
In order to test this, we first tested the anti-inflammatory effects of soluble DXM on human macrophages. Peripheral blood mononuclear cells (PBMCs) were isolated from human healthy donors and we differentiated them into macrophages. Macrophages were treated with different concentrations of soluble DXM (0.01, 0.03 and 0.09μM) or DMSO control 30 min before M0 (no stimulation) or M1 (LPS+ IFN-gamma) polarization. After 24 hours, supernatants and RNA were collected. ELISA was used to quantify secretion of pro-inflammatory cytokines IL-6, IL-12, and TNF-alpha. Real-Time PCR was used to determine changes in pro-inflammatory genes expression.
Results showed an overall decrease in inflammatory cytokines when treated with soluble DXM when compared to DMSO. IL-6, TNF-α, IL-12, and IL-1β were decreased by all three concentrations. The 0.09 μM of soluble DXM showed the biggest decrease. We conclude that 0.09 μM is the optimal dose of DXM to reduce pro-inflammatory macrophages. We are currently testing DXM in Ace-DEX microparticles to see if transporting DXM into macrophages has the same, if not better, anti-inflammatory effect. Preliminary data indicate that targeting DXM to macrophages with AceDEX particles has similar anti-inflammatory effects. These results suggest that use of AceDEX particles may be beneficial in MS by suppressing inflammatory cytokines.”