低劑量砷及中波紫外線對角質細胞凋亡的交互作用

Effects and Interactions of Low Doses of UVB and Arsenic on Keratinocyte Apoptosis

李志宏(Chih-Hung Lee)

指導教授 ： 陳國熏 ； 余幸司

高雄醫學大學/醫學院/醫學研究所/碩士(2003年)

摘要

砷引起的波文氏症大部分出現在皮膚的非光照部位，此外，過去的實驗顯示中波紫外線的照射會抑制波文氏症病灶的增生。因此，中波長紫外線對砷的致癌性可能有調控的作用。本實驗的目的是研究低劑量砷及中波長紫外線對培養角質細胞的細胞週期、凋亡、和p53、p21Cip1/WAF1、及Bcl-2/Bax蛋白質的作用及低劑量砷及中波長紫外線兩者對上述作用的交互影響。培養的角質細胞以砷化鈉1微莫耳合併中波長紫外線50 mJ/cm2作各類的處理，包括正常組、只加砷(As組)、只照射中波長紫外線(UVB組)、先加砷再照射中波長紫外線(As-UVB組)、先照射中波長紫外線再以砷處理(UVB-As組)。細胞週期分析及的結果發現所有有處理組均產生S期遲滯；而含溴尿苷酸攝取(BrdU uptake)的結果發現As-UVB組和UVB-As組有生長遲滯的現象。以TUNEL方法偵測凋亡發現As-UVB組、UVB組、UVB-As組都有凋亡的現象，而最高的凋亡率出現在UVB-As組。西方墨點分析的結果發現p53出現在As-UVB組，其他組沒有發現。p21Cip1/WAF1在所有實驗組都有上昇的現象，並且以As-UVB組最明顯。Bcl-2在UVB組、As-UVB組和UVB-As組都有下降的現象，且以As-UVB組和UVB-As組最明顯。在As-UVB組中增加的p53與解釋角質細胞的生長遲滯多於凋亡有關。而在UVB-As組中p21Cip1/WAF1的上昇和Bcl-2的下降可能和角質細胞的凋亡有關。不管是先加砷或後加砷合併中波長紫外線照射都有造成角質細胞生長抑制和凋亡的效果，這可以解釋皮膚砷癌多出現在非光照部位的原因，以及提供中波長紫外線照射對砷有關之波文氏症的治療機轉。

關鍵字

砷 ； 紫外線 ； 角質細胞 ； 波文氏病 ； 凋亡

並列摘要

Although arsenic and ultraviolet B are both causal factors for skin cancers, lesions of arsenic-induced Bowen’s disease are often confined to sun-protected areas. Ultraviolet B may play a modulatory role in arsenic-carcinogenesis. The purpose of this study was to evaluate the effects and interaction of arsenic and ultraviolet B on cell cycle progression, apoptosis and expressions of p53, p21Cip1/WAF1, and Bcl-2 proteins. Cultured keratinocytes were treated with sodium arsenite (1 mM) and/or ultraviolet B 50 mJ/cm2 exposures in different combinations, including arsenic alone, UVB alone, arsenic than UVB (As-UVB), and UVB then arsenic (UVB-As) treatments. Cell cycle analysis and BrdU-pulsing revealed S-phase arrest in all treatment groups and growth arrest in As-UVB and UVB-As groups. TUNEL assay showed a higher apoptosis rate in UVB-As group as compared to that of As-UVB and UVB groups. Results of western blotting demonstrated increased p53 in As-UVB group but not in others. P21Cip1/WAF1 expressions were increased in all treatment groups but highest in As-UVB group. Bcl-2 was lowest in As-UVB and UVB-As group. Increase p53 in As-UVB group may explain the growth retardation rather than apoptosis in this group. P21Cip1/WAF1 upregulation and Bcl-2 downregulation were related to apoptosis in UVB-As group. In either event, the antiproliferative and proapoptotic effect of ultraviolet B on arsenic-treated keratinocytes may provide the therapeutical basis of UVB on arsenic-related Bowen’s disease and the explanation of rare occurrence of arsenic skin cancers in sun-exposed area. P53 may play a pivotal role in the interactions of arsenic and UVB in cultured keratinocytes.

並列關鍵字

arsenic ； ultraviolet ； keratinocyte ； Bowen's disease ； apoptosis

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