Realgar-mediated growth inhibition on HaCaT human keratinocytes is associated with induction of apoptosis.

School of Chinese Medicine, Faculty of Science, Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong, PR China.
International Journal of Molecular Medicine (Impact Factor: 1.88). 09/2009; 24(2):189-96.
Source: PubMed

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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tetra-arsenic tetra-sulfide (As4S4) is an arsenic compound with anti-tumor activity, especially in acute promyelocytic leukemia (APL) that are resistant to retinoic acid (RA). Although recent studies revealed that the therapeutic action of As4S4 is closely associated with the induction of cellular apoptosis, the exact molecular mechanism of action of As4S4 in RA-resistant APL remains to be clarified. In this study, we found that As4S4-induced apoptosis was accompanied by reduced mRNA and protein expression of SET gene in RA-resistant NB4-R1 cells. Moreover, RNAi knockdown of SET gene further promoted As4S4-induced apoptosis, while SET over-expression inhibited it, suggesting that As4S4 induces apoptosis through the reduction of SET protein in NB4-R1 cells. We also demonstrated that the knockdown of SET gene resulted in the upregulation of protein phosphatase 2 (PP2A) expression and the downregulation of promyelocytic leukemia and retinoic acid receptor α fusion gene (PML-RARα) expression, which were enhanced by As4S4 treatments. By contrast, over-expression of SET gene resulted in PP2A downregulation and PML-RARα upregulation, which were abolished by As4S4 pretreatment. Since PP2A is a pro-apoptotic factor and PMLRARα is an anti-apoptotic factor, our results suggest that As4S4-induced apoptosis in NB4-R1 cells is through the downregulation of SET protein expression, which in turn increases PP2A and reduces PML-RARα expressions to lead to cell apoptosis.
    PLoS ONE 01/2014; 9(1):e83184. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, QUE, but not the structurally related chemical, rutin, enhanced the cytotoxicity of arsenic trioxide (As(+3)) against the viability of normal human HaCaT keratinocytes via induction of apoptosis. QUE enhancement of As(+3)-mediated apoptosis was accompanied by increased intracellular peroxide production according to a DCFH-DA analysis, and DNA ladders induced by QUE/As(+3) were inhibited by adding the antioxidative compound, N-acetyl cysteine (NAC). A loss of the mitochondrial membrane potential by QUE/As(+3) was observed according to DiOC(6) staining in concert with increased Bax protein and cytosolic cytochrome (Cyt) c protein expression in HaCaT cells, which was prevented by the addition of NAC. A decrease in the p53 protein with increased protein ubiquitination was detected in QUE/As(+3)-treated HaCaT cells, and this was prevented by the addition of NAC. The decrease in the p53 protein by QUE/As(+3) was reversed by adding the proteasome inhibitor, MG132. L-Buthionine sulphoximine (BSO) enhanced the cytotoxicity of As(+3) against the viability of HaCaT cells with reduced p53 protein through inducing protein ubiquitination and reactive oxygen species (ROS) production, and disrupting the mitochondrial membrane potential in HaCaT cells. Additionally, QUE and BSO enhanced the cytotoxic effects of monomethylarsonous acid (MMA(+3)) but not other arsenic compounds in accordance with increased p53 protein ubiquitination in HaCaT cells. QUE plus As(+3) stimulation of apoptosis in human HaCaT keratinocytes via activating ROS-dependent p53 protein ubiquitination may offer a rationale for the use of QUE to improve the clinical efficacy of arsenics in treating psoriasis.
    Experimental Dermatology 05/2012; 21(5):370-5. · 4.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract As2S2 has been traditionally used to treat certain types of leukemia. However, detailed action mechanism of As2S2 was not sufficiently documented. The effects of As2S2 on HL-60 cells were investigated by focusing on proliferation, differentiation, generation of reactive oxygen species (ROS), intracellular glutathione (GSH) depletion, and activation of p38 mitogen activated protein kinase (MAPK). As2S2 at 0.5-8μM induced cell differentiation based on the increment in CD11b expression, nitroblue tetrazolium (NBT)-positive cells, and cell size change. A transient increase in ROS level along with intracellular GSH level was also observed. p38 MAPK activation gradually increased after ROS generation and sustained during the cell differentiation. Decreased CD11b expression was accompanied by p38 MAPK activation, and p38 MAPK inhibitor restored the CD11b expression. The results suggest that moderate levels of oxidative stress induced by As2S2 correlate with HL-60 cell differentiation. Suppression of p38 MAPK can augment the efficacy of As2S2 to induce HL-60 cell differentiation.
    Leukemia & lymphoma 05/2013; · 2.61 Impact Factor