Risperidone effects on heterochromatin: the role of kinase signaling

Summary Epigenetic effects of anti‐psychotic medications are poorly understood. We have appropriated a model whereby heterochromatin is established through 24‐ or 48‐h lipopolysaccharide (LPS) treatment, and tested the epigenetic effects of risperidone along the adenylyl cyclase/protein kinase A (AC/PKA) pathway in human liposarcoma cells that express the LPS‐sensitive Toll‐like receptor (TLR)‐4. Human SW872 cells were cultured with LPS and mRNA expression levels and epigenetic modifications of dimethylated lysine 9 of histone 2 (H3K9me2), geterochromatin protein 1γ (HP1γ) and phospho‐H3S10 at promoters of interleukin (IL)‐6, tumor necrosis factor (TNF)‐α and IL1β were measured. Pharmacological manipulation of the AC/PKA pathway was achieved through treatment with a PKA inhibitor (H89), mitogen‐ and stress‐activated kinase 1 (MSK1) inhibitor (SB‐747651A) or forskolin. Twenty‐four and 48‐h LPS treatment establishes heterochromatin at selected promoters, corresponding to decreased mRNA expression. Concurrent risperidone treatment with LPS treatment can both ‘block’ and ‘reverse’ heterochromatin formation. Forskolin treatment resulted in a similar disassembling effect on heterochromatin. Conversely, inhibition of PKA by H89 or MSK1 both blocked ‘normalizing’ effects of risperidone on LPS‐induced heterochromatin. Our results demonstrate that risperidone can disassemble heterochromatin, exerting this effect along the G‐protein/AC/PKA pathway. This approach can also be utilized to investigate functional outcomes of single or combined pharmacological treatments on chromatin assemblies in human cells.