Trichostatin C

Cone photoreceptor loss is the main cause of color blindness and loss of visual acuity in patients suffering from inherited cone dystrophies. Despite the crucial role of cones in everyday life, knowledge on mechanisms of cone cell death and the identification of potential targets for the preservation or delay of cone loss are scarce. Recent findings have shown that excessive histone deacetylase (HDAC) activity is associated with both primary rod and primary cone degeneration. Importantly, pharmacological inhibition of HDAC activity in vivo at the onset of cone degeneration offers a prolonged protection of cones in a mouse model of inherited cone degeneration (cpfl1). In this study, we evaluated the potential of trichostatin A (TSA), a pan-HDAC inhibitor, to prevent cone cell death at a later stage of degeneration in the cpfl1 model. We demonstrate that a single intravitreal TSA injection protected the cpfl1 cones even when administered after the onset of degeneration. In addition, the TSA treatment significantly improved aberrant cone nucleokinesis present in the cpfl1 retina. These results highlight the feasibility of targeted cone neuroprotection in vivo even at later disease stages of inherited cone dystrophies.

Histone deacetylase inhibitors such as sodium butyrate or (R)-trichostatin A {(R)-TSA; 7- [4-(dimethylamino) phenyl]-N-hydroxy-4,6-dimethyl-7-oxo-2, 4-heptadienamide} have been reported to modulate the proliferation and differentiation of certain cell types. In this study, we analyzed the effects of these agents on KM12 human colon carcinoma (HCC) cells in culture. We found that (R)-TSA induced cell flattening, inhibited anchorage-dependent and anchorage-independent growth, increased the level of the differentiation marker carcinoembryonic antigen, and increased the expression of gelsolin, a candidate tumor suppressor, in these HCC cells. Cells treated with (R)-TSA for 3 h exhibited a high degree of histone (primarily H4) acetylation. (R)-TSA exerted these effects at concentrations in the range between 0.1 to 1 mu M that are at least 1,000 times lower than those required to achieve similar effects by n-butyrate. Trichostatin C, which exhibits some histone deacetylase inhibitory activity but not the analogs (S)-TSA or (R)- or (S)-trichostatic acid, which lack histone deacetylase inhibitory activity, also showed some growth inhibitory activity. These results indicate that histone deacetylase inhibitors may lead to suppression of the transformed phenotype and enhanced differentiation in the KM12 HCC cells.

Cigarette smoke causes lung tumorigenesis; however, the mechanisms underlying transformation are unknown. We investigated if tobacco compounds induce DNA promoter hypermethylation in BEAS-2B cells treated with low doses of cigarette smoke condensate (CSC) for one month. Transcriptional profiles and anchorage-independent growth were explored using Affymetrix microarray and soft agar assay, respectively. To investigate if tobacco compounds induce hypermethylation, CSC/dimethyl sulfoxide (DMSO)-treated cells were further treated with 5-Aza-2'-deoxycytidine (5AzaC) and trychostatin A (TSA). This treatment was followed by transcriptional profiling. CSC-exposed cells acquired a fibroblast-like shape with enhanced anchorage-independent growth. Silencing of epithelial cadherin, the hallmark of epithelial to mesenchymal transition (EMT), was observed upon exposure to CSC. Changes in the expression of genes involved in epidermal development, intercellular junction formation, and cytoskeleton formation were identified. Gene expression profiles from 5AzaC- and TSA-treated cells revealed 130 genes possibly methylated due to chronic CSC exposure. Our results suggest that E-cadherin may also be silenced by hypermethylation in an in vitro model of chronic exposure to low doses of CSC. This study demonstrates evidence for a tobacco compound induced EMT-like process in vitro and provides insight into possible mechanisms of gene silencing occurring during this treatment.