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Arsenic compounds have been traditionally used to treat a variety of ailments, including skin diseases. Our previous study identified the extract of realgar to possess potent antiproliferative action on HaCaT cells. The present study aimed at evaluating whether several inorganic arsenics found in realgar also possess similar antiproliferative properties. The results showed that arsenic trioxide, arsenic pentoxide, and arsenic iodide had significant antiproliferative action on HaCaT cells, with IC 50 values at 2.4, 16, and 6.8 M, respectively. However, these compounds only modestly inhibited the growth of Hs-68 cells, a normal human skin fibroblast cell line, with IC 50 values at 43.4, 223, and 89 M, respectively, conferring a favorable toxicity profile. In mechanistic studies, all three compounds caused DNA fragmentation as demonstrated by gel electrophoresis and the terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling method. Morphologically, nuclear condensation and DNA fragmentation were observed when the cells were exposed to arsenic compounds. Cell cycle analysis with propidium iodide (PI) staining demonstrated the appearance of sub-G 1 peak and cell arrest at the G 1 phase in the presence of these compounds. Quantitative analysis by annexin V-PI staining revealed that the arsenic-induced apoptotic event was dose-dependent. Moreover, the arsenic compounds were able to activate caspase-3 expression when examined by Western blot analysis. Our experimental data unambiguously demonstrated that induction of cellular apoptosis was mainly responsible for the observed antiproliferation brought about by the arsenic compounds on HaCaT keratinocytes, suggesting that these arsenic compounds are putative agents from which psoriasis-treating topical formulae could be developed.Arsenics are inorganic metalloids that are ubiquitously distributed throughout the Earth's crust. For centuries, some of these inorganic compounds have been used to treat a variety of ailments in many traditional medical systems. In Chinese medicine, for example, arsenic-containing minerals are primarily prescribed for the topical treatment of scabies, carbuncles, herpes zoster, enduring ulcers, psoriasis, and arthritis (Jiangsu New Medical College, 1986;Hua et al., 2003). In our previous study, realgar, a mineral commonly used in Chinese medicine for topical treatment of psoriasis and the main chemical constituent of which is As 2 S 2 , was found to be a potent antiproliferative agent on HaCaT cells (Tse et al., 2006). This promising experimental finding stimulated us to further investigate whether other arsenic compounds also possess similar antiproliferative properties. The identification of active antiproliferative arsenics and the elucidation of their action mechanism would lead to the development of topical agents for effective management of psoriasis.Affecting approximately 2% of the population worldwide, psoriasis is a common chronic inflammatory skin disease (Lebwohl, 2003;Nickoloff and Nestle, 2004). Histologically,...

Psoriasis is a skin disease associated with hyperproliferation and aberrant differentiation of keratinocytes. Our previous studies have identified the root of Rubia cordifolia L. as a potent antiproliferative and apoptogenic agent in cultured HaCaT cells (IC(50) 1.4 microg/ml). In the present study, ethanolic extract of Radix Rubiae was fractioned sequentially with hexane, ethyl acetate (EA), n-butanol and water. EA fraction was found to possess most potent antiproliferative action on HaCaT cells (IC(50) 0.9 microg/ml). Mechanistic study revealed that EA fraction induced apoptosis on HaCaT cells, as it was capable of inducing apoptotic morphological changes. Annexin V-PI staining assay also demonstrated that EA fraction significantly augmented HaCaT apoptosis. In addition, EA fraction decreased mitochondrial membrane potential in a concentration- and time-dependent manner. The standardized EA fraction was formulated into topical gel and its keratinocyte-modulating action was tested on mouse tail model. EA fraction dose-dependently increased the number and thickness of granular layer and epidermal thickness on mouse tail skin, indicative of the keratinocyte differentiation-inducing activity. Taking the in vitro and in vivo findings together, the present preclinical study confirms that EA fraction is a promising antipsoriatic agent warranting further development for psoriasis treatment.

Psoriasis is a chronic inflammatory skin disease characterized histologically by hyperproliferation and aberrant differentiation of epidermal keratinocytes. While screening 60 psoriasis-treating Chinese herbs for their anti-proliferative properties using a cultured human HaCaT keratinocyte model, we found Radix Rubiae to be highly effective. Evidence is now provided that induction of apoptosis is the underlying mechanism for the observed anti-proliferative action of Radix Rubiae. Analysis of cell cycle with PI staining showed that Radix Rubiae induced the appearance of a sub-G1 peak and cell arrest at the G1 phase. Radix Rubiae was also capable of inducing morphological changes as evidenced by nuclear condensation. DNA fragmentation was clearly demonstrated by gel electrophoresis and by the TUNEL method. Quantitative analyses by Annexin V-PI staining revealed that Radix Rubiae-induced apoptosis was dose-and timedependent. Furthermore, Radix Rubiae was able to activate caspase-3 expression when examined by Western blot analysis. The cellular, morphological and molecular data unequivocally demonstrated that induction of cellular apoptosis was mainly responsible for the previously observed anti-proliferation induced Radix Rubiae on HaCaT keratinocytes. Our experimental results suggest that Radix Rubiae is a promising source from which a herb-based topical agent could be developed for psoriasis treatment.

Abstract. Traditional Chinese medicine has long been used to treat a variety of ailments including skin diseases. Our previous study has revealed the ethanolic extract of realgar, a common ingredient used in psoriasis treatment in Chinese medicine, to possess potent anti-proliferative action on cultured HaCaT cells of human keratinocyte origin. In the present study, the mechanisms of action of the observed growth inhibitory action of realgar were investigated. Several bioassay methods were employed to elucidate whether cellular apoptosis is involved in the realgar-induced growth inhibition of the skin cells. Morphologically, nuclear condensation and DNA fragmentation were observed when HaCaT cells were exposed to the realgar extract. DNA fragmentation induced by the treatment of realgar was also evident as detected by gel electrophoresis and the TUNEL method. Cell cycle analysis by propidium iodide (PI) staining demonstrated the appearance of sub-G1 peak and cell cycle arrest at the G1 phase upon realgar treatment. Quantitative analysis by annexin V-PI staining revealed that the realgar-induced apoptotic event was dose-dependent. Furthermore, realgar was able to activate caspase-3 expression when examined by Western blot analysis. Our experimental data unambiguously confirm that induction of cellular apoptosis is mainly responsible for the observed growth inhibition brought about by realgar on the HaCaT keratinocytes, and this finding helps place the traditional use of this mineral for psoriasis treatment on a scientific footing.

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