Effects of the antipsoriatic drug dithranol on E2A and caspase-9 gene expression in vitro

Although the precise causes of psoriasis remain to be elucidated, psoriasis has been known as a disorder in which factors in the immune system, enzymes and other biochemical substances that regulate skin cell division are functionally imbalanced, thereby resulting in rapid proliferation of keratinocytes and incomplete keratinization. The expression of candidate genes such as E2A and caspase-9, which have been recognized to play a critical role in cellular proliferation/differentiation and apoptosis, is of great interest. They may be therapeutically targeted by the antipsoriatic drug, dithranol. We examined the molecular effects of dithranol on the mRNA and protein expression levels of E2A and caspase-9 in the HaCaT keratinocyte cell line. The HaCaT cells were treated with 0-0.5 μg/mL dithranol for 30 min. After dithranol was washed out, the HaCaT cells were cultured for 2 h, and their total cellular RNA and proteins were isolated. Quantitative real-time reverse transcriptase-polymerase chain reaction and Western blot were performed to determine the mRNA and protein levels of these two genes. We found that dithranol treatment in the range of 0.25-0.5 μg/mL slightly upregulated the mRNA expression of E2A and caspase-9 approximately 1.5- and 1.2-fold, respectively. However, undetectable change and minor downregulation of the protein expression levels were observed for E2A and caspase-9, respectively. Consequently, these genes appear not to be viable therapeutic targets for dithranol.