Effects Of Arsenic On Cell Proliferation And Apoptosis In Human Epidermal Keratinocytes And Investigation Of Mechanisms Of Its Carcinogenesis

Arsenics have been used to treat syphilis, psoriasis, asthma and arthritis in clinic, as well as application in the fields of industry and agriculture. People decreased gradully to apply them due to the recognization of arsenic carcinogenicity and mutagenicity. In recent years, arsenics have been under intense and extensive investigation in two aspects. First, arsenic trioxide (As2O3) and arsenic sulfide (As4S4) have been shown to be effective in the treatment of acute promyelocytic leukemia(APL), these studies promote people to research wether As2O3 might induce apoptosis of other tumor cellls. Second, investigation of arsenic carcinogenic mechanism.Lissauer treated APL with solution of potassium arsenite in 1865. The application of arsenic was reduced after 1950's, mainly because of its carcinogenicity and the appearance of new chemotherapy medicines. As2O3 ,in a protocal originally developed in Hargbin, China, was recently confirmed to be an effective treatment for APL in patients who relapsed after chemotherapy and all-trans retinoic acid treatment. Shanghai institute of hematology suggest As2O3 induce cell apoptosis ,downregulate bcl-2 gene in NB4 and HL60 cell lines. Recent reports showed that As2O3 might induce apoptosis and inhibit cell growth in malignant lymphoid cell lines, as well as in myeloma cells and other hematopoietic precursors, moreover in solid tumor cells, such as neuroblastomas cell lines, gastric carinoma cell lines, esophageal carcinoma cells. We investigated the effects of As2O3 on cell proliferation and apoptosis in keratinocytes in vitro because it was reported As2O3 had an antitumoral effect in skin cancer.On the other hand, inorganic arsenic is a recognized human carcinogen. Exposure via the drinking water, medicinal agents, or occupational exposure is associated with an increased risk for skin cancer and various internal caners. Less severe dermatological effects, including skin hyperpigmentation and hyperkeratosis.A high rate of these disease have been reported in patients receiving Fowler's solution for the treatment of psoriasis in the 1960s to 1970s, yet the mechanism is not clear. It was reported that arsenite treatment led to enhanced DNA synthesis and induction of cell proliferation. Arsenic induce over expression of TGF-(, EGF and GM-CSF, enhence the activity of AP-1 and NFkappaB, which play a significant role in inflammation and arsenic-induced skin cancer. In the last few years, investigators in abroad pay more attention to signal transduction pathways invoved in cell proliferation and transformation., In the present study, we investigated effects of arsenic trioxide (As2O3) on cell proliferation and apoptosis in human epidermal keratinocytes: cell line HaCat and A431. At the same time, we verify and explore the mechanism of arsenic carcinogenesis through observing the cytokine secretion, DNA synthesis and gene expression of E2F, ERK associated with cell proliferation. Part Ⅰ Effects of Arsenic Trioxide on Cell Proliferation and Apoptosis in Human Epidermal KeratinocytesObjective To investigate the effects of arsenic trioxide on cell proliferation and induction of apoptosis in human epidermal keratinocytes. Methods Human benign epidermal keratinocytes (cell line HaCaT), human carcinoma cells(cell line A431) were cultured . After treatment of both kinds of cells with arsenite, the growth inhibition effect was determined by measuring MTT dye absorbence of living cells. Apoptosis was assessed with respect to morphological changes by light and electron microscopic examinations and to cell cycle distribution by flow cytometry , annexin-ⅴbinding assay was used to detect the early stage of apoptosis. Results Ranging from 0.5μM to 10μM , arsenic trioxide significantly inhibited the proliferation of HaCaT cells in a dose- and time-dependent manner. By light and electron microscopic examination, morphological changes show the characteristic of apoptosis. But A431 cells hadn't obvious change. DNA flow cytometric analysis indicated that arsenic t...