Schallreuter Karin U, Hasse Sybille, Rokos Hartmut, Chavan Bhaven, Shalbaf Mohamed, Spencer Jennifer D, Wood John M
Clinical and Experimental Dermatology, Division of Biomedical Sciences, School of Life Sciences, University of Bradford, Bradford BD7 1DP, UK.
Exp Dermatol. 2009 Aug;18(8):680-8. doi: 10.1111/j.1600-0625.2009.00850.x. Epub 2009 Mar 7.
Cholesterol is important for membrane stability and is the key substrate for the synthesis of steroid hormones and vitamin D. Furthermore, it is a major component of the lipid barrier in the stratum corneum of the human epidermis. Considering that steroid hormone synthesis is taking place in epidermal melanocytes, we tested whether downstream oestrogen receptor/cAMP signalling via MITF/tyrosine hydroxylase/tyrosinase/pigmentation could be possibly modulated by cholesterol. For this purpose, we utilized human primary melanocyte cell cultures and human melanoma cells with different pigmentation capacity applying immunofluorescence, RT-PCR, Western blotting and determination of melanin content. Our in situ and in vitro results demonstrated that melanocytes can synthesize cholesterol via HMG-CoA reductase and transport cholesterol via LDL/Apo-B100/LDLR. Moreover, we show that cholesterol increases melanogenesis in these cells and in human melanoma cells of intermediate pigmentation (FM55) in a time- and dose-dependent manner. Cellular cholesterol levels in melanoma cells with different pigmentation patterns, epidermal melanocytes and keratinocytes do not differ except in the amelanotic (FM3) melanoma cell line. This result is in agreement with decreasing cholesterol content versus increasing pigmentation in melanosomes. Cholesterol induces cAMP in a biphasic manner i.e. after 30 min and later after 6 and 24 h, meanwhile protein expression of oestrogen receptor beta, CREB, MITF, tyrosine hydroxylase and tyrosinase is induced after 72 h. Taken together, we show that human epidermal melanocytes have the capacity of cholesterol signalling via LDL/Apo-B100/LDL receptor and that cholesterol under in vitro conditions increases melanogenesis.
胆固醇对膜稳定性很重要，是合成甾体激素和维生素D的关键底物。此外，它是人类表皮角质层脂质屏障的主要成分。鉴于甾体激素合成发生在表皮黑素细胞中，我们测试了胆固醇是否可能通过MITF/酪氨酸羟化酶/酪氨酸酶/色素沉着对下游雌激素受体/cAMP信号传导进行调节。为此，我们利用具有不同色素沉着能力的人原代黑素细胞培养物和人黑素瘤细胞，应用免疫荧光、RT-PCR、蛋白质印迹法和黑色素含量测定。我们的原位和体外结果表明，黑素细胞可以通过HMG-CoA还原酶合成胆固醇，并通过LDL/Apo-B100/LDLR转运胆固醇。此外，我们表明胆固醇以时间和剂量依赖性方式增加这些细胞和中度色素沉着的人黑素瘤细胞（FM55）中的黑素生成。除了无色素（FM3）黑素瘤细胞系外，具有不同色素沉着模式的黑素瘤细胞、表皮黑素细胞和角质形成细胞中的细胞胆固醇水平没有差异。这一结果与黑素小体中胆固醇含量降低与色素沉着增加一致。胆固醇以双相方式诱导cAMP，即在30分钟后以及随后在6小时和24小时后，同时雌激素受体β、CREB、MITF、酪氨酸羟化酶和酪氨酸酶的蛋白质表达在72小时后被诱导。综上所述，我们表明人表皮黑素细胞具有通过LDL/Apo-B100/LDL受体进行胆固醇信号传导的能力，并且在体外条件下胆固醇会增加黑素生成。
