Trichostatin A (TSA) is an organic compound that serves as an antifungal antibiotic and selectively inhibits the class I and II mammalian histone deacetylase (HDAC) families of enzymes, but not class III HDACs (i.e., sirtuins).

TSA can be used to alter gene expression by interfering with the removal of acetyl groups from histones (histone deacetylases, HDAC) and therefore altering the ability of DNA transcription factors to access the DNA molecules inside chromatin.

It is a member of a larger class of histone deacetylase inhibitors (HDIs or HDACIs) that have a broad spectrum of epigenetic activities.

HDIs have multiple effects on non-histone effector molecules, so the anti-cancer mechanisms are truly not understood at this time.

[7] TSA represses IL (interleukin)-1β/LPS (lipopolysaccharide)/IFNγ (interferon γ)-induced nitric oxide synthase 2 (NOS2) expression in murine macrophage-like cells but increases LPS-stimulated NOS2 expression in murine N9 and primary rat microglial cells.