蛋白激酶B和丝裂原活化蛋白激酶在烟酸保护的HaCaT细胞抵抗中波紫外线损伤中的作用

目的 探讨烟酸保护由UVB诱导的角质形成细胞损伤的胞内信号传导分子机制。 方法 UVB照射和烟酸处理HaCaT细胞,TUNEL法检测细胞凋亡,Western印迹检测蛋白激酶B（Akt）/丝裂原活化蛋白激酶（MAPK）通路相关蛋白Akt、P38、JNK、ERK1/2的磷酸化水平变化。ELISA检测细胞分泌内皮素1（ET-1）及碱性成纤维细胞生长因子（bFGF）的水平。结果 Western印迹结果表明,UVB照射和烟酸处理HaCaT细胞后,p-Akt、p-P38、p-JNK、p-ERK1/2蛋白在60 min内都显著激活（P < 0.01）。烟酸预处理后的HaCaT细胞再经UVB照射,可以发现p-Akt、p-P38、p-ERK1/2信号分子在2 h内激活更显著（P < 0.01）。３个抑制剂加UVB照射组较3个单独抑制剂组ET-1、bFGF表达降低,差异均有统计学意义,其中LY294002组、SB203580组ET-1、bFGF水平最低;烟酸预保护的抑制剂处理组HaCaT细胞在UVB照射后,LY294002和U0126组没有出现ET-1、bFGF水平回升,SB203580组bFGF水平出现回升。结论　Akt信号分子在烟酸保护的HaCaT细胞抵抗UVB损伤中起一定的调控作用。     

中波紫外线通过EGFR/PI3K/AKT途径上调HaCaT细胞转铁蛋白受体的表达

目的 探讨中波紫外线辐射对HaCaT转铁蛋白受体表达的影响及其信号途径。方法 流式细胞仪检测HaCaT细胞转铁蛋白受体的表达。实时PCR检测转铁蛋白受体mRNA表达。结果 UVB辐射可上调HaCaT细胞转铁蛋白受体mRNA及其蛋白的表达，并在一定范围内（10 mJ/cm2 ~ 30 mJ/cm2）呈剂量依赖性。表皮生长因子受体（EGFR）抑制因子PD153035、磷脂酰肌醇3激酶（PI3K）抑制因子LY294002和渥曼青霉素（wortmannin）均可显著抑制UVB辐射对转铁蛋白受体的上调作用（P < 0.01）。结论 紫外线可通过EGFR/PI3K/AKT途径上调HaCaT 细胞转铁蛋白受体的表达。     

中波紫外线诱导HaCaT细胞凋亡的研究

目的以不同剂量的中波紫外线(UVB)诱导体外培养的人永生化角质形成细胞(HaCaT细胞)凋亡,探讨肿瘤坏死因子-α(TNF-α)是否参与凋亡过程。方法取对数生长期的HaCaT细胞,分别用10 mJ/cm2,15 J/cm2,20 J/cm2,25 J/cm2,30 J/cm2的UVB照射,并于照射24 h后检测HaCaT细胞的增殖活性,分析HaCaT细胞的凋亡率,测定HaCaT细胞上清液中TNF-α的水平,观察细胞形态及凋亡细胞特征。结果在10~30 mJ/cm2的UVB照射下,随照射剂量的增大,细胞的增殖活性逐渐下降,而细胞的凋亡率逐渐增加,当剂量达30 J/cm2时,细胞凋亡率最大,细胞的增殖活性和凋亡率呈直线负相关;随UVB照射剂量的增大,TNF-α的分泌量增加,细胞上清液中TNF-α的分泌量和凋亡率呈直线正相关;倒置显微镜及透射电镜进一步从形态学上证实了细胞的凋亡改变。结论UVB可诱导细胞凋亡,且呈剂量依赖性;照射产生的TNF-α可能参与了其凋亡过程。     

中波紫外线通过EGFR／P13K／AKT途径上调HaCaT细胞转铁蛋白受体的表达

目的探讨中波紫外线辐射对HaCaT转铁蛋白受体表达的影响及其信号途径。方法流式细胞仪检测HaCaT细胞转铁蛋白受体的表达。实时PCR检测转铁蛋白受体mRNA表达。结果UVB辐射可上调HaCaT细胞转铁蛋白受体mRNA及其蛋白的表达，并在一定范围内（10mJ／cm^2-30mJ／cm^2）呈剂量依赖性。表皮生长因子受体（EGFR）抑制因子PD153035、磷脂酰肌醇3激酶（P13K）抑制因子LY294002和渥曼青霉素（Wortmannin）均可显著抑制UVB辐射对转铁蛋白受体的上调作用（P〈0．01）。结论紫外线可通过EGFR／P13K／AKT途径上调HaCaT细胞转铁蛋白受体的表达。     

曲克芦丁对UVB诱导HaCaT细胞损伤的保护作用

目的研究曲克芦丁对中波紫外线(UVB)诱导的HaCaT细胞光损伤的保护作用及机制。方法将培养的HaCaT细胞分为空白对照组、UVB组、曲克芦丁组、曲克芦丁+UVB组。其中UVB组、曲克芦丁+UVB组予50m J/cm~2的UVB照射,曲克芦丁组、曲克芦丁+UVB组分别加入不同浓度的曲克芦丁干预。用CCK-8法检测细胞增殖能力。Hoechst染色法检测细胞凋亡。Western blot法检测丝裂原活化蛋白激酶(MAPK)信号通路相关蛋白p-P38,p-JNK,p-ERK,以及激活蛋白-1(AP-1)的组件c-Fos,c-Jun的表达情况。结果 CCK-8法提示,5~10μmol/L的曲克芦丁对UVB诱导的HaCaT细胞光损伤有较好的保护作用(P0.05)。Hoechst染色显示,UVB组凋亡细胞较空白对照组增多,曲克芦丁+UVB组凋亡细胞较UVB组减少。Western blot法提示UVB照射后HaCaT细胞p-P38,p-ERK,p-JNK,p-c-Jun及c-Fos水平升高,曲克芦丁+UVB组有不同程度下降。结论曲克芦丁对UVB诱导的HaCaT细胞光损伤有一定的保护作用。     

双氢睾酮对HaCaT细胞SREBP-1c表达的影响

目的 探讨双氢睾酮（DHT）在HaCaT细胞固醇调控元件结合蛋白-1c（SREBP-1c）表达中的作用。 方法 体外培养HaCaT细胞,分为4组,对照组不加任何刺激因素,DHT组分别加入3种不同浓度的DHT,LY294002 + DHT组在加入50 μmol/L PI3K抑制剂（LY294002）预处理40 min后加入100 nmol/L DHT,PD98059 + DHT组即在加入50 μmol/L MEK抑制剂（PD98059）预处理40 min后加入100 nmol/L DHT。用实时定量PCR和Western印迹法检测DHT对HaCaT细胞SREBP-1c mRNA和蛋白表达的影响。Western印迹法检测DHT作用于HaCaT细胞后蛋白激酶B（AKT）、胞外信号调控激酶（ERK）、p38丝裂原活化蛋白激酶（p38 MAPK）、c-Jun氨基末端激酶（JNK）的磷酸化情况。 结果 DHT可呈浓度依赖性上调HaCaT细胞SREBP-1c mRNA和蛋白的表达,并诱导AKT、ERK的磷酸化,但对p38、JNK的磷酸化无明显激活作用。LY294002预处理后HaCaT细胞SREBP-1c mRNA的表达较单纯DHT组明显降低（t = 9.406,P < 0.05）;SREBP-1蛋白水平降为0.7113 ± 0.0313,与单纯DHT组2.2577 ± 0.0601比较,差异有统计学意义（t = 39.498,P < 0.05）。而PD98059预处理后,SREBP-1c mRNA和蛋白的表达与单纯DHT组比较,差异均无统计学意义（P > 0.05）。结论 DHT可诱导HaCaT细胞SREBP-1c mRNA和蛋白的表达。     

绿茶提取物及羟氯喹对表皮细胞光保护生物学效应的研究

目的观察羟氯喹及没食子儿茶素没食子酸脂(EGCG)对中波紫外线(UVB)照射引起的人永生化角质形成细胞系HaCaT细胞增殖活性变化及凋亡的影响。方法采用剂量分别为0、30、60、90mJ/cm~2的UVB照射培养的HaCaT细胞并加入羟氯喹及EGCG,共孵育24h后以四甲基偶氮唑蓝还原法(MTT)检测细胞活性,流式细胞仪检测细胞周期和凋亡率变化。结果UVB照射后HaCaT细胞出现增殖活性下降,其幅度与辐射强度成正比;加入羟氯喹及EGCG可使细胞活性有一定程度恢复;此外,UVB照射可诱导HaCaT细胞产生凋亡,凋亡率呈UVB剂量依赖方式增加;30mJ/cm~2UVB照射可使HaCaT细胞出现明显S期阻滞,随UVB剂量增大,S期细胞数量相对下降;加入药物处理可抑制上述改变。结论羟氯喹和EGCG可明显抑制UVB引起的HaCaT细胞增殖活性下降、凋亡与细胞周期阻滞。     

安石榴苷对中波紫外线诱导HaCaT细胞光损伤的预防作用研究

目的 探讨安石榴苷对中波紫外线（UVB）诱导角质形成细胞损伤的保护机制。 方法 培养的HaCaT细胞分为空白对照组、安石榴苷组、UVB组、安石榴苷 + UVB组。噻唑蓝（MTT）法检测细胞增殖能力,Hoechst/碘化丙锭（PI）染色和流式细胞仪检测细胞凋亡,RT-PCR法测定金属基质蛋白酶1（MMP1）及其组织抑制因子1（TIMP1） mRNA表达水平,Western印迹检测丝裂原活化蛋白激酶（MAPK）通路相关蛋白P38、JNK、ERK的磷酸化水平变化。 结果 MTT试验示,10 ～ 40 μmol/L安石榴苷对UVB诱导的HaCaT细胞损伤有较佳的预保护作用。UVB组HaCaT细胞强Hoechst和强PI双染细胞较空白对照组增多,安石榴苷 + UVB组较UVB组减少。流式细胞仪分析,UVB组凋亡细胞百分率（9.82% ± 0.11%）高于空白对照（1.24% ± 0.91%,P < 0.01）,而安石榴苷（10、20、40 μmol/L） + UVB组凋亡细胞百分率（分别为6.38% ± 0.14%、5.24% ± 0.17%、3.77% ± 0.11%）较UVB组低,差异有统计学意义（均P < 0.01）。UVB组MMP1 mRNA相对表达量（12.376 ± 0.602）高于空白对照组（1.007 ± 0.147,P < 0.01）,而TIMP1 mRNA相对表达量（0.103 ± 0.006）低于空白对照组（1.006 ± 0.139,P < 0.01）,安石榴苷组MMP1及TIMP1 mRNA与空白对照组比较,差异无统计学意义（均P > 0.05）。安石榴苷预处理的HaCaT细胞经30 mJ/cm2 UVB照射后MMP1 mRNA相对表达量较UVB组降低（均P < 0.01）,而TIMP1 mRNA较UVB组升高（均P < 0.01）。Western印迹示,经UVB照射后,HaCaT细胞p-ERK、p-JNK及p-p38表达升高（均P < 0.01）。安石榴苷组HaCaT细胞p-ERK、p-JNK及p-p38表达没有明显改变（P > 0.05）,而安石榴苷 + UVB组有不同程度下降（均P < 0.01）。 结论 安石榴苷对UVB引起HaCaT细胞损伤有一定的预防作用。     

中波紫外线对HaCaT细胞凋亡、细胞周期变化及p16、c-myc蛋白表达的影响及阿魏酸干预作用研究

目的观察传统中药川芎的有效成份阿魏酸(ferulic)对中波紫外线(UVB)辐射引起的人表皮角质形成细胞系HaCaT细胞凋亡、细胞周期及对p16、c-myc蛋白水平变化的影响,以探讨其光保护作用与机制。方法培养HaCaT细胞,以不同剂量UVB和200mg/mL浓度的阿魏酸处理细胞,以流式细胞仪检测0、30、60和90mJ/cm~2的UVB照射后24h细胞周期和凋亡率变化;以Western blot方法检测30mJ/cm~2UVB照射后p16、c-myc蛋白的表达水平。结果UVB照射诱导HaCaT细胞产生凋亡,凋亡率呈UVB剂量增加而升高;30mJ/cm~2剂量下细胞可出现明显S期阻滞,但高剂量时S期细胞数量相对下降;照光后p16、c-myc蛋白水平均增高。加入阿魏酸处理可抑制UVB引起的上述改变。结论阿魏酸可明显抑制UVB引起的凋亡与细胞周期阻滞以及p16、c-myc蛋白表达。     

双氢青蒿素对UVB诱导的人皮肤HaCaT细胞凋亡的保护作用

目的:明确双氢青蒿素(DHA)对UVB诱导人皮肤HaCaT细胞凋亡的保护作用。方法:将体外培养的HaCaT细胞分为空白对照组,UVB照射组和UVB+DHA(20、40、60、80μmol/L)组,采用MTT法检测细胞系的增殖情况,流式细胞仪检测细胞的凋亡率,RT-PCR法检测抗凋亡基因survivin和促凋亡基因caspease-3(激活型)mRNA水平,Western检测相关蛋白表达水平。结果:30 mJ/cm~2 UVB照射24 h后,UVB组和UVB+DHA(20、40、60、80μmol/L)组细胞的增殖率分别为空白对照组的(50.13±2.42)%,(60.23±2.30)%,(69.24±3.19)%,(79.37±2.47)%和(70.41±2.24)%。UVB组和UVB+60μmol/L DHA组中HaCaT细胞凋亡率分别为(46.7±3.2)%和(23.71±1.2)%。与UVB组比较,UVB+60μmol/L DHA组中HaCaT细胞caspase-3 mRNA及蛋白表达降低、survivin mRNA及蛋白表达升高。结论:DHA可抑制UVB所致HaCaT细胞的凋亡,其机制可能与survivin和caspase-3有关。     

紫外线调节血管内皮生长因子分泌机制的研究

目的：探讨中波紫外线（UVB）增强血管内皮生长因子（VEGF）分泌的信号途径。方法：采用流式细胞仪检测表皮生长因子受体（EGFR）和磷酸化EGFR表达。ELISA检测上清液中VEGF水平。结果：UVB照射后15min可以检测到磷酸化EGFR表达．30min时达最高峰,1h开始下降,2～8h降至基础水平,而EGFR表达量不变。UVB（30mJ／cm^2）分别照射EGFR^＋/-、EGFR^＋/＋和EGFR^-/-小鼠胚胎成纤维细胞（MEF）,结果显示EGFR^＋/＋MEF组VEGF分泌明显高于EGFR^＋/-MEF组和EGFR^-/-MEF组,UVB对EGFR^-/--MEF的VEGF分泌促进作用不明显。EGFR磷酸化酶抑制因子PD153035可明显抑制VEGF分泌,1μmol／L有抑制作用,5μmol／L抑制作用增强。磷脂酰肌醇3激酶（PI3K）高度选择性抑制剂LY294002及不可逆抑制剂wortmannin均可明显抑制VEGF分泌。结论：紫外线通过EGFR—PI3K-蛋白激酶（AKT）途径增强VEGF分泌。     

TNF-alpha impairs the S-G2/M cell cycle checkpoint and cyclobutane pyrimidine dimer repair in premalignant skin cells: role of the PI3K-Akt pathway

Tumor necrosis factor-alpha (TNF-alpha) is induced by UVB radiation and has been implicated in the early stages of skin carcinogenesis. Here, we show that in normal keratinocytes and the transformed keratinocyte cell lines, HaCaT and A431, TNF-alpha stimulates protein kinase B/Akt, which results in activation of the survival complex mTORC1 (mammalian target of rapamycin complex 1) and inhibition of the proapoptotic proteins Bad and FoxO3a. In UVB-irradiated HaCaT cells (10-20 mJ cm(-2)), TNF-alpha increased the proportion of cycling cells and enhanced the rate of apoptosis. A significantly higher proportion of UVB-treated HaCaT cells containing unrepaired cyclobutane pyrimidine dimers (CPDs) escaped the G2/M cell cycle checkpoint in the presence of TNF-alpha (9.5+/-3.3 vs 4.8+/-2.2%). After treatment with the PI3K inhibitor LY294002, only 1.2+/-0.7% of CPD-containing HaCaT cells were actively cycling. TNF-alpha enhanced apoptosis less potently and did not increase the level of CPD or stimulate cell cycle progression in normal keratinocytes. Our data suggest that TNF-alpha overrides the G2/M checkpoint in premalignant skin cells and allows for some cells containing unrepaired CPD to enter the cell cycle. The effect of TNF-alpha seems to be dependent on Akt activation and may constitute a relevant mechanism enhancing mutagenesis and tumor development.     

Involvement of EGF receptor activation in the induction of cyclooxygenase-2 in HaCaT keratinocytes after UVB

Because selective inhibition of cyclooxygenase-2 (COX-2) suppressed the induction of skin tumors in mice by UV and as UV has been shown to induce expression of COX-2 in skin and cells, COX-2 may be crucial for photocarcinogenesis of the skin. We studied the mechanism of UVB-induced expression of COX-2 focusing on the signal transduction pathway involved. Hydrogen peroxide (H2O2) treatment of HaCaT cells induced expression of COX-2 and pretreatment with the antioxidant N-acetylcysteine (NAC) partly inhibited the UVB-induced expression of COX-2 protein in HaCaT cells, suggesting that oxidative stress contributes to COX-2 induction. To examine the signaling pathways involved in the UVB-induced expression of COX-2 in HaCaT cells, we analysed the expression of COX-2 protein after treatment with various inhibitors of signaling molecules. Inhibition of EGFR by a specific inhibitor and by a neutralizing antibody suppressed the induction of COX-2 expression by UV. Although a neutralizing antibody to transforming growth factor-alpha (TGF-alpha) suppressed COX-2 expression induced by TGF-alpha, it did not suppress COX-2 expression by UV, indicating that a direct activation of EGFR is involved. Treatment of cells at low temperature (4 degrees C) inhibited UVB-induced JNK activation, but it did not inhibit COX-2 expression by UV. Inhibitors of MEK, p38 MAP kinase and PI3-kinase, suppressed the induction of COX-2 expression by UV. In contrast, an erbB-2 inhibitor augmented the UVB-induced increase of COX-2 protein. These data indicate that oxidative stress in association with activation of EGFR, ERK, p38 MAP kinase, and PI3-kinase plays crucial roles in the UVB induction of expression of COX-2.     

001: hepatocyte growth factor/scatter factor inhibits UVB induced apoptosis of human keratinocytes via the PI-3-kinase pathway

UVB-irradiation induces apoptosis in primary keratinocytes (KC) and KC-derived cell-lines A431 and HaCaT. Here we report on the inhibition of UV induced KC-apoptosis by hepatocyte growth factor/scatter factor (HGF/SF). The protective effect of HGF/SF for UVB-irradiated primary KC was observed at concentrations as low as 1 ng/ml HGF and was confirmed by demonstration of the inhibition of nucleosome-release and the activation of caspase-3. In contrast to the observation with primary KC HGF/SF had no effect on the survival of A431 and HaCaT cells after UVB-irradiation, despite the fact that we could demonstrate that these cells functionally express the HGF/SF receptor c-met. When blocking signalling pathways initiated by c-met, we found that the inhibition of the phosphatidylinositol-3-OH (PI-3) kinase by wortmannin or LY294002 led to a total inhibition of the anti-apoptotic effect of HGF/SF, whereas the blockade of the MAP-kinase pathway by PD90859 had no effect. This represents the first demonstration of an involvement of the PI-3 kinase pathway in the anti-apoptotic effect of HGF/SF. In conclusion, our data demonstrate that HGF/SF is able to rescue KC but not autonomously growing KC cell lines from apoptosis induced by UVB. Since in vivo HGF/SF is produced by mesenchymal cells, this mechanism may represent an important paracrine loop in the skin supporting the survival of KC after UV-injury.     

Suppression of mTOR complex 2-dependent AKT phosphorylation in melanoma cells by combined treatment with rapamycin and LY294002

Background  Inhibition of mTOR complex 1 (mTORC1) with rapamycin leads to phosphorylation of AKT in some cancer cells, with unknown biological consequences. The role of this phosphorylation in melanoma is unknown, although preliminary clinical data indicate poor activity of rapalogues in melanoma.
Objectives  We aimed at elucidating the role of AKT phosphorylation after mTORC1 inhibition in melanoma cells.
Methods  Western blotting, apoptosis assays, cell cycle analyses and viability assays were performed to analyse the effects of rapamycin and LY294002 treatment on melanoma cells. For suppression of mTOR complex 2 (mTORC2) an siRNA directed against rictor was used.
Results  Rapamycin showed limited effects on cell viability but resulted in strong and lasting AKT phosphorylation in melanoma cells. Combined PI3K/mTOR inhibition with LY294002 had pronounced effects on viability but also led to increased AKT phosphorylation after prolonged treatment. In contrast, combination of rapamycin plus LY294002 suppressed AKT phosphorylation. Suppression of AKT phosphorylation did not correlate with decreases in cell viability. Inhibition of mTORC2 led to reduced levels of phosphorylated AKT.
Conclusions  mTORC1 inhibition with rapamycin and with LY294002 can lead to AKT phosphorylation in melanoma cells via mTORC2. Combination of rapamycin and LY294002 suppresses AKT phosphorylation but without significant effect on treatment efficacy.     

Negative feedback regulation of phosphatidylinositol 3-kinase/Akt pathway by over-expressed cyclooxygenase-2 in human epidermal cancer cells

While enhanced expression of cyclooxygenase (COX)-2 has been observed in human skin epidermal cancer, the mechanisms underlying COX-2 expression have not been completely elucidated. Recently, a role for the phosphatidylinositol-3 (PI3) kinase pathway in COX-2 expression has attracted attention. We investigated COX-2 expression, PI3 kinase activity, and the phosphorylation level of Akt, a downstream effector of PI3 kinase, in the human skin cancer cell line HSC-5. Compared to the nontumorigenic keratinocyte HaCaT, in HSC-5 cells, COX-2 protein expression and PI3 kinase activity were increased. The PI3 kinase inhibitor LY294002 reduced COX-2 expression in HSC-5 cells and, contrary to our expectation, the phosphorylation of Akt was significantly decreased. The expression of Bcl-2, which is regulated by Akt, was reduced, and apoptosis was induced in HSC-5 cells compared to HaCaT cells. COX-2 inhibitor NS398 up-regulated Akt phosphorylation. These results imply that constitutively over-expressed COX-2 down-regulates the Akt phosphorylation through a negative feedback mechanism.