Original Articles
Natapong Kawjit, Thitiporn Cha
Abstract
Recognized as an incurable disease, psoriasis is a chronic inflammatory disease, which is characterized by hyperproliferation and abnormal differentiation of keratinocytes. Although psoriasis has become a public health concern, its precise causes remain to be elucidated. The current study aimed at evaluating the suppressive effect of each of these following Thai plant extracts with anti-psoriatic activity, Alpinia galanga L. (rhizome), Curcuma longa L. (rhizome) and Annona squamosa L. (leaf), on the expression of the helix-loop-helix transcription factor Id1 (inhibitor of differentiation or inhibitor of DNA binding), which is known as a biomarker for psoriasis. In addition, we would like to assess their antioxidant contents and activities in order to provide insights into the mechanism underlying the inhibitory effect. Using confocal immunofluorescence technique, we found that the expression of Id1 protein was clearly reduced upon treating the HaCaT cells with 6.3, 3.15 or 1.575 μg/ml (IC50= 6.3μg/ml) of Annonas quamosa leaf extract. Western blot analysis confirmed that the Id1 protein was significantly attenuated after treating HaCaT cells with all tested concentrations of ethanolic extract of Annona squamosa leaves (P<0.05). No inhibitory effect of Alpinia galanga and Curcuma longa extracts on the Id1 expression was observed. Regarding antioxidant contents and antioxidant activities, although it exhibited the inhibitory effect on the Id1 expression, the extract of Annona squamosa was not the richest. This suggests that the suppressive effect of Annona squamosa extract may not be primarily responsible by antioxidant contents and activities.