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Original Article

Exp Neurobiol 2018; 27(5): 437-452

Published online October 31, 2018

© The Korean Society for Brain and Neural Sciences

HDAC3 Inhibition Promotes Alternative Activation of Macrophages but Does Not Affect Functional Recovery after Spinal Cord Injury

Selien Sanchez1,†, Stefanie Lemmens1,†, Paulien Baeten1, Daniela Sommer1, Dearbhaile Dooley2, Sven Hendrix1,‡*, and Myriam Gou Fabregas1,‡

1Department of Morphology, Biomedical Research Institute, Hasselt University, Diepenbeek BE3590, Belgium.

2Health Science Centre, School of Medicine, University College Dublin, Dublin D04 V1W8, Ireland.

Correspondence to: *To whom correspondence should be addressed.
TEL: 32 11 26 92 46
Equally contributing first authors.
Equally contributing senior authors.

Received: July 4, 2018; Revised: September 7, 2018; Accepted: September 28, 2018

After spinal cord injury (SCI), monocyte derived macrophages play a detrimental role. Histone deacetylases (HDACs) are central epigenetic regulators of macrophage-polarization. We hypothesized that HDAC3 inhibition suppresses the pro-inflammatory macrophage phenotype (M1), promotes the anti-inflammatory phenotype (M2) and improves functional recovery after SCI. Therefore, two inhibitors of HDAC3 were selected, namely scriptaid and RGFP966. The impact on macrophage polarization was studied by investigating the effect on gene and protein expression of selected M1 and M2 markers. We show that scriptaid differentially influences M1 and M2 markers. It increases CD86 and iNOS gene expression and decreases GPR18, CD38, FPR2 and Arg-1 gene expression as well as the production of IL-6 and NO. RGFP966 primarily increased the expression of the M2 markers Arg-1 and Ym1 and reduced the production of IL-6 (M1). RGFP966 and scriptaid reduced the formation of foamy macrophages. Finally, to investigate the impact of HDAC3 inhibition on functional recovery after SCI, we studied the effects of RGFP966 and scriptaid in an in vivo T-cut hemisection SCI model. Histological analyses were performed on spinal cord sections to determine lesion size and astrogliosis, demyelinated area and selected infiltrating immune cells. RGFP966 and scriptaid did not affect functional recovery or histopathological outcome after SCI. In conclusion, these results indicate that specific HDAC3 inhibition with RGFP966 promotes alternative activation of macrophages and reduces the formation of foamy macrophages, but does not lead to a better functional recovery after SCI.

Graphical Abstract

Keywords: HDAC3, Spinal cord injury, Macrophages, RGFP966 and Scriptaid