中波紫外线辐射对原代及永生化角质形成细胞损伤能力的比较研究

目的：观察原代角质形成细胞和永生化HaCaT角质形成细胞对中波紫外线照射的反应差异。方法：采用不同剂量中波紫外线(UVB)照射上述两种细胞，评估UVB对细胞作用的时间及剂量效应，以倒置光学显微镜观察细胞受损程度，MTT法检测细胞活性。结果：UVB照射后，细胞损伤程度均随照射剂量加大而加重；另经24h、48h及72h孵育后，对两种细胞进行不同时间段的细胞活性(MTT)比值比较(72h／24h，72h／48h)：分别为原代角质形成细胞(1．16和1.63)和HaCaT细胞(0．96和0．91)。MTT结果显示低剂量紫外线照射时，细胞损伤恢复可发生在照射后48h；高剂量紫外线照射后，两种细胞的损伤程度均随孵育时间延长而加重。结论：原代角质形成细胞抵抗紫外线照射损伤的能力较强，而HaCaT细胞相对较易受损。     

Induction of apoptosis by synthetic ceramide analogues in the human keratinocyte cell line HaCaT

Abstract: In contrast to extracellular, long chain ceramides which comprise a structural component of the epidermal water barrier, intracellular ceramides originating from sphingomyelin hydrolysis have been shown to inhibit proliferation and to induce apoptosis in different cell populations. To further elucidate the possible role of intracellular ceramides in human epidermis, two new cell-permeable ceramide analogues, N -thioacetylsphingosine (C₂-Cer=S) and 4-dodecanoylamino-decan-5-ol (FS-5), were synthesized and tested for their ability to suppress cell growth and to induce apoptosis in immortalized human keratinocytes. It was shown that the well-investigated ceramide analogue N -acetylsphingosine (C₂-Cer=O), as well as the new compound C₂-Cer=S inhibited proliferation of HaCaT cells with half-inhibitory concentrations (IC₅₀) of 20 μg/ml and 10 μg/ml, respectively, whereas FS-5 has been potent with an IC₅₀>40 μg/ml. Overall, all three ceramide analogues induced apoptosis in HaCaT cells as assessed by DNA-fragmentation using ELISA technique and in situ nick end labelling, thereby confirming the importance of ceramide signalling in keratinocytes.     

Thrombin and melittin activate phospholipase C in human HaCaT keratinocytes

Abstract Following the activation of specific receptors, phospholipase C has been shown to cleave the membrane phospholipid phosphatidylinositol bisphosphate into the 2nd messengers inositol 1,4,5-trisphosphate and di-acylgiycerol. Both 2nd messengers contribute to the regulation of cellular proliferation. The receptor for bradykinin is coupled to this pathway in keratinocytes, but knowledge about other activators of phospholipase C is limited. Additional mediators and agents were therefore examined regarding their ability to activate phospholipase C in HaCaT keratinocytes. Analysis for ³H-inositol phosphates was performed by anion-exchange HPLC. Thrombin and melittin induced a time- and dose-dependent release of inositol 1,4,5-trisphosphate. Several other mediators examined such as angiotension II, neurotensin, C3a, pituitary adenylate cyclase activating peptide, phenylephrin, and prostaglandin E₂, did not induce the formation of inositol phosphates. In view of the mitogenic activity and the increased formation of thrombin after tissue injury, the coupling of the thrombin receptor to phospholipase C in HaCaT keratinocytes suggests a rôle of this protease in epidermal wound healing.     

Lipid composition and synthesis of HaCaT cells, an immortalized human keratinocyte line, in comparison with normal human adult keratinocytes

Abstract Cultured keratinocytes are frequently employed for studies of epidermal lipid metabolism. Interpretation of experimental data may be complicated by donor to donor variability, the relatively short culture lifetime and variations between passages, problems thai are not encountered to the same extent with immortalized cell lines. The present study was undertaken to compare the lipid composition and synthesis of normal human adult keratinocytes (NHAK) with HaCaT cells, a long-lived. spontaneously immortalized human keratinocyte line, in relation to proliferation and differentiation. No differences between the two cell types were observed: a) in total lipid content; b) in the distribution of major lipid classes during growth at 50%, 75% and 100% confluence: c) in cultures grown at 0.6 mM calcium, at which differentiation is retarded, or at 1.6 mM calcium, at which some differentiation takes place; d) in the incorporation of [¹⁴C] acetate into cellular lipids at confluence, or e) in the fatty acid composition of major cellular lipid classes. At 100% confluence NHAK and HaCaT cells differ in their cholesterol metabolism. At all stages of growth, cholesterol synthesis in HaCaT cells is more LDL-dependent than in NHAK. Furthermore, NHAK become less LDL-dependent at confluence whereas HaCaT cells do not. HaCaT cells also revealed a significantly larger fraction of phosphatidyl-ethanolamine, -serine and -inositol at 0.6 mM calcium concentration than NHAK. These findings suggest that HaCaT cells do not differentiate as well as NHAK in vitro and may therefore serve as a model for the study of lipid metabolism in cells defective in terminal differentiation.     

Effects of extracellular calcium on the growth-differentiation switch in immortalized keratinocyte HaCaT cells compared with normal human keratinocytes

Abstract:  The keratinocyte growth and differentiation switch, tightly regulated by several mechanisms, is generally associated with decreased proliferation, cell cycle arrest in G0/G1 phase and expression of epidermal differentiation markers, such as keratin 1 (K1), keratin 10 (K10) and involucrin. In vitro , the spontaneously immortalized human keratinocyte cell line HaCaT is often used as a model to study keratinocyte functions. Comparative differentiation studies between HaCaT cells and normal human keratinocytes (NHK) over an extended time-period have rarely been reported. Therefore, we studied their switch from a proliferating to a differentiated state over 13 days. As culture conditions involved changes in cellular responses, cells were cultured in a specific medium for keratinocyte growth and differentiation was induced by increasing extracellular calcium concentration from 0.09 to 1.2 m m . In NHK, addition of calcium-induced morphological changes and concomitant decreased proliferation. For HaCaT cells, calcium addition resulted in morphological changes, but in an unexpected manner, cells were more proliferative than when cultured at low calcium levels. HaCaT cell hyperproliferation correlated with cell cycle analysis, showing an accumulation in S/G2-M phases. Furthermore, RT-PCR and western blot analysis revealed a delay in the expression of the differentiation markers K1, K10 and involucrin in HaCaT cells compared with NHK. In conclusion, even though calcium-induced differentiation was not associated with a decreased cell proliferation, HaCaT cells conserved properties characteristic of differentiation.     

Inositol phosphate formation and release of intracellular free calcium by bradykinin in HaCaT keratinocytes

Phospholipase C-mediated release of inositol trisposphate, followed by an increase in free intracellular calcium, is an important signal transduction pathway for several membrane receptors. In the present investigation, the coupling of various receptors to phospholipase C was studied in the human keratinocyte line HaCaT. Inositol trisphosphate formation was determined by anion-exchange chromatography, and the release of intracellular calcium was analysed with the fluorescence probe Fura-2 AM. Activation of HaCaT keratinocytes with bradykinin resulted in a time- and dose-dependent release of inositol trisphosphate and intracellular calcium, with an EC₅₀ value of 50 nM for bradykinin-induced inositol trisphosphate formation. The mediators and cytokines IL-1, IL-4, IL-6, IL-8, EGF and TGF, as well as bombesin, prolactin, carbachol, substance P and retinoic acid, did not activate this pathway. The inability of the mediators examined to activate phospholipase C may be due to lack of the respective cognate receptors or to the use of other signal transduction pathways.     

Protein kinase C isozymes regulate proliferation and high cell density-mediated differentiation in HaCaT keratinocytes

Protein kinase C (PKC) isoforms play pivotal roles in the regulation of differentiation of normal human epidermal keratinocytes (NHEK). In this study, we investigated the participation of the PKC system in the proliferation and high cell density-induced differentiation of the human immortalized keratinocyte line HaCaT. HaCaT keratinocytes possessed a characteristic PKC isoform pattern (PKC alpha, beta, gamma, delta, epsilon, eta, theta, zeta), which altered during proliferation and differentiation. The GF109203X compound, a selective PKC inhibitor, suppressed the expressions of the lat (granular cell) differentiation markers involucrin (INV) and filaggrin (FIL), and the terminal marker keratinocyte-specific transglutaminase-1 (TG), but did not affect the level of the early (spinous cell) marker keratin 10 (K10) and cellular proliferation. Phorbol 12-myristate 13-acetate (PMA), an activator of PKC, inhibited proliferation, elevated intracellular calcium concentration, decreased the expression of K10, and increased the expressions of INV, FIL, and TG. These data indicate that the endogenous activation of PKC regulates the expressions of the late differentiation markers, and that the exogenous activation of PKC by PMA results in the induction of terminal differentiation. Because the cellular effects of PMA were accompanied by differential down-regulations of the sensitive PKC isoforms in proliferating and differentiating cultures, our findings argue for the differential roles of the existing PKC isoforms in the regulation of cellular proliferation and high cell density-induced differentiation of HaCaT cells.     

瘦素调节HaCaT细胞角蛋白17的表达

目的 探讨瘦素对HaCaT细胞角蛋白17（K17）表达的影响。 方法 体外培养HaCaT细胞,给予100 ng/ml的瘦素作用24 h,应用实时PCR检测K17 mRNA表达水平、Western印迹及免疫荧光染色法检测K17蛋白表达水平变化。 结果 与阴性对照组（1.000 0 ± 0.000 0）相比较,瘦素组（3.086 7 ± 0.186 1）K17 mRNA表达显著升高,差异有统计学意义（P < 0.01）。Western印迹结果表明,瘦素组K17蛋白较阴性对照组显著上调,细胞免疫荧光染色结果与RT-PCR、Western印迹结果相符。与单纯使用瘦素组（2.242 7±0.188 7）相比较,STAT3抑制剂组和Erk1/2抑制剂组K17 mRNA分别为0.674 1 ± 0.060 0、0.855 0 ± 0.390 3,Western印迹和细胞免疫荧光染色显示,两个抑制剂组的K17蛋白较瘦素组均显著下调,差异均有统计学意义（P < 0.01）。 结论 瘦素可以诱导HaCaT细胞表达K17,其机制可能与激活STAT3、Erk1/2信号转导途径有关。     

Differential modulation of stress-inflammation responses by plant polyphenols in cultured normal human keratinocytes and immortalized HaCaT cells

Background

Environmental and endogenous stresses to skin are considered causative reasons for skin cancers, premature ageing, and chronic inflammation. Screening of substances with preventive and/or curative properties is currently based on mechanistic studies of their effects towards stress-induced responses in skin cell cultures.

Objective

We compared effects of plant polyphenols (PPs) on the constitutive, UVA-, LPS-, or TNF-alpha-induced inflammatory responses in cultured normal human epidermal keratinocytes (NHEK) and immortalized HaCaT cells.

Methods

Representatives of three classes of PPs, flavonoids, stilbenoids, and phenylpropanoids were studied. Their effects on mRNA were determined by qRT-PCR; protein expression was assayed by Western blot and bioplexed ELISA; phosphorylation of Akt1, ERK1/2, EGFR, and NFkappaB was quantified by intracellular ELISA or Western blot.

Results

PPs or their combination with UVA or LPS induced strong up-regulation of stress responses in HaCaT but not in NHEK. In addition, compared to NHEK, HaCaT responded to TNF-alpha with higher synthesis of MCP-1, IP-10 and IL-8, concomitant with stronger NFkappaB activation. PPs down-regulated the chemokine release from both cell types, although with distinct effects on NFkappaB, Akt1, ERK, and EGFR activation.

Conclusion

Results of pharmacological screenings obtained by using HaCaT should be cautiously considered while extending them to primary keratinocytes from human epidermis.     

Quercetin enhancement of arsenic-induced apoptosis via stimulating ROS-dependent p53 protein ubiquitination in human HaCaT keratinocytes

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.     

芍药苷对UVB所致HaCaT细胞凋亡的防护作用

目的：明确芍药苷对UVB所致HaCaT细胞凋亡的防护作用。方法：将HaCaT细胞分为8组,A组：空白对照组;B组：UVB照射对照组; C～H组分别为0.25mg/L, 0.5 mg/L,1 mg/L,2.5 mg/L,5 mg/L及10 mg/L芍药苷预处理组,均照射UVB。用流式细胞术检测细胞凋亡情况,RT-PCR检测P21mRNA的表达水平。结果：B组细胞凋亡率为4.840±0.836明显高于C～G组（0.423±0.179、1.127±0.535、1.633±0.417、 2.570±0.439、3.137±0.347）（P<0.05）。 B组与H组（4.203±0.655）比较,差异无统计学意义（P >0.05）;B组P21mRNA表达为1.040±0.007明显高于C～H组（0.440±0.015、0.551±0.013、0.857±0.017、0.848±0.027、0.850±0.052、0.923±0.035）（P<0.05）。结论：芍药苷在一定浓度内（0.25 mg～5 mg/L）对UVB致HaCaT细胞的凋亡有保护作用,并能减少P21mRNA的表达。     

Distribution of IL-18 and IL-18 receptor in human skin: various forms of IL-18 are produced in keratinocytes

Abstract Human interleukin-18 (IL-18) enhances IL-12-mediated IFN-γ production by lymphocytes and Fas/ perforin-mediated cytolysis by NK cells. IL-18 is synthesized as a 24 kDa proform, and the proform is processed in the cytoplasm into an 18 kDa mature form. Active and precursor forms of IL-18 have been detected in immunocompetent cells, and active IL-18 exerts its functions through its receptor. We sought to determine which human skin cells are responsible for production of IL-18 and which express its receptor. Monoclonal antibodies against human IL-18 and polyclonal antibody against IL-18 receptor were provided for this analysis. Formalin-embedded and frozen sections of human epidermis were analyzed by immunoperoxidase and immunofluorescence staining. IL-18 was detected in all living cell layers of the epidermis, hair follicles, arrectores pilorum, eccrine ducts and endothelial cells. IL-18 was localized in the cytoplasm of cells in living epidermal cell layers. In contrast, IL-18 receptor was mainly detected in keratinocytes and expressed in the cell periphery in living cell layers. Since keratinocytes were the main source of IL-18 and its receptor, cultured human keratinocytes were further analyzed by immunoblotting. IL-18 receptor was identified as an 80 kDa single band. The mature 18 kDa and precursor 24 kDa forms of IL-18 were detected by our monoclonal antibody (mAb) 21 and mAb 132, respectively, while only the 18 kDa form was detected by a commercial mAb, 125-2H. Cultured keratinocytes showed positive granular staining for IL-18 in the cytoplasm and positive staining for IL-18 receptor mainly in the cell periphery. Our findings indicate that mature IL-18, precursor IL-18 and IL-18 receptor are simultaneously expressed with different localizations by human epidermal keratinocytes. Keratinocytes might be activated by their own IL-18 in an autocrine or paracrine fashion. Received: 14 August 2000 / Revised: 10 December 2000 / Accepted: 24 April 2001     

Differential effects of UV irradiation on nuclear retinoid receptor levels in cultured keratinocytes and melanocytes

A major risk factor for skin cancer is UV irradiation, which not only damages DNA and other photosensitive compounds like vitamin A, but may also perturb cellular signaling, e.g. via the retinoid receptor system believed to be important for cancer protection. We used cultured normal human keratinocytes and melanocytes to examine the effects of UV irradiation on the expression of the predominant retinoid receptors in the human skin (RARalpha, RARgamma and RXRalpha) and the AP-1 protein c-Jun; mRNA levels were studied by real-time PCR and protein levels by Western blot. In keratinocytes, a single dose of UVB (50 mJ/cm2) caused a rapid drop in the expression of all three receptors (mRNA levels minus 35-50% after 4 h; protein levels minus 20-45% after 8 h), which was followed over the next 40 h by a variable response, leading to full normalization for RARalpha only. In contrast, the levels of c-Jun did not change significantly after UV exposure. In melanocytes, UVB caused a similar drop of the retinoid receptor levels as in keratinocytes but this was soon followed by an increased expression leading to a complete normalization of all receptor levels within 1-3 days. The c-Jun levels in melanocytes increased 1 day after UV exposure and remained high (plus 50%) thereafter. In both cell types, a approximately 3-fold increase in apoptosis (measured by DNA fragmentation) was observed 8-48 h after UVB irradiation. In conclusion, a depletion of vitamin A and retinoid receptors by UV irradiation, together with unchanged or even increased c-Jun levels, might seriously interfere with retinoid signaling and thus promote future tumor development, especially in keratinocytes.     

EGCG对中波紫外线诱导HaCaT细胞p53基因和蛋白表达的实验研究

目的:研究表没食子儿茶素没食子酸酯(EGCG)对中波紫外线(UVB)照射诱导永生化角质形成细胞株-HaCaT细胞的p53 mRNA和p53蛋白表达的影响。方法:以一定剂量UVB照射HaCaT细胞,并以200μg/mL EGCG处理照射后的HaCaT细胞,分别用RT-PCR法和Western blot方法检测各处理条件下p53 mRNA和/或p53蛋白的表达水平。结果:30 mJ/cm2的UVB照射后HaCaT细胞的p53 mR-NA和p53蛋白表达逐渐增加,4 h达到峰值,4 h后随照射剂量增加而增加,24 h后有所恢复;加入EGCG可下调UVB诱导的表达作用。结论:UVB照射对HaCaT细胞p53 mRNA和p53蛋白的诱导表达有时效性与量效性,EGCG可下调UVB照射的这种诱导作用。     

The expression of keratinocyte growth factor receptor (FGFR2-IIIb) correlates with the high proliferative rate of HaCaT keratinocytes

Keratinocyte growth factor receptor (KGFR = FGFR2-IIIb) is a tyrosine kinase receptor expressed by keratinocytes, which mediates the effects of fibroblast growth factors (FGF). There are contradictory data in the literature regarding the role of FGFR2-IIIb during the proliferation/differentiation programme of keratinocytes. In this study, we aimed to investigate whether overexpression of FGFR2-IIIb may have a role in the regulation of keratinocyte proliferation. We analysed the expression of FGFR2-IIIb in an in vitro HaCaT model system representing different stages of proliferation and differentiation of keratinocytes. Real-time RT-PCR and Western blot analyses demonstrated a correlation between FGFR2-IIIb mRNA and protein expression and the proportion of cells in S/G2/M phase in synchronized HaCaT keratinocytes and thus with proliferation activity (r = 0.96). After treatment with the antipsoriatic drug, dithranol, FGFR2-IIIb is downregulated dose dependently both at mRNA and protein levels. Moreover, when the rate of proliferation is decreased by the lack of cell attachment to the culturing surface, FGFR2-IIIb mRNA (P = 0.0315) and protein expressions were also reduced (P = 0.0242), while a differentiation marker, keratin 10, mRNA (P = 0.0003) and protein levels (P = 0.001) were increased (r = -0.92). Based on our results we conclude that FGFR2-IIIb expression in HaCaT keratinocytes corresponds with the proliferative activation of the cells and is not related to the differentiation programme.     

瘦素通过激活STAT3信号通路促进HaCaT细胞增殖

【摘要】 目的 探讨瘦素对人角质形成细胞的生物学作用及其分子机制。 方法 以人永生化角质形成细胞系HaCaT细胞为研究对象,不同浓度人重组瘦素处理细胞,CCK-8法检测瘦素对细胞增殖影响,流式细胞仪检测细胞周期变化,Western印迹分析瘦素激活的下游信号分子活化程度。采用GraphPad Prism 5 软件进行统计分析,组间差异采用t检验。 结果 CCK-8法检测显示,50 μg/L及100 μg/L瘦素作用24及48 h后可使细胞增殖活性不同程度增加,且瘦素在24 h内的促增殖效应呈剂量依赖方式（r = 0.9989,P < 0.05）。流式细胞仪检测发现,与未经瘦素处理的对照组相比,100 μg/L瘦素作用24 h后S期细胞比例增多,而G0/G1期细胞比例减少;处理组细胞增殖指数为0.603 ± 0.0157,显著高于对照组（0.564 ± 0.0144）,差异有统计学意义（P < 0.05）。Western印迹发现,100 μg/L瘦素可使HaCaT细胞STAT3的磷酸化程度明显增高。STAT3抑制剂piceatannol能明显抑制瘦素刺激的HaCaT细胞促增殖作用。 结论 瘦素可能通过激活STAT3信号转导途径促进角质形成细胞增殖。     

Inhibitors of cysteine cathepsin and calpain do not prevent ultraviolet-B-induced apoptosis in human keratinocytes and HeLa cells

Caspases, members of the cysteine protease family, execute UVB-induced apoptosis in several cell lines and keratinocytes. Several researchers investigating UVB-induced apoptosis have demonstrated a dose-dependent protective effect of the synthetic peptide caspase inhibitor zVAD-fmk. However, zVAD-fmk displays a dose-dependent protective effect against UVB-induced apoptosis, even at doses higher than those required to block all known proapoptotic caspases. In addition, it is known that zVAD-fmk also inhibits other cysteine proteases including cathepsins and calpains, and these proteases have recently been demonstrated to play a role in the execution of programmed cell death induced by other stimuli, e.g. TNF-α. The purpose of the present study was therefore to investigate whether inhibitors of cysteine cathepsins and calpains could prevent UVB-induced apoptosis in HeLa cells and keratinocytes. This was done by investigating the effect of the irreversible cysteine protease inhibitor zFA-fmk, the cathepsin B inhibitor CA-074-Me and the calpain inhibitor ALLN on the viability of UVB-irradiated human keratinocytes and HeLa cells. At concentrations of 10 μM and above zVAD-fmk conferred partial dose-dependent protection against UVB-induced apoptosis in HeLa cells and keratinocytes. Moreover, caspase-3 activity was completely blocked at zVAD-fmk concentrations of 1 μM in HeLa cells. This indicates that caspase-independent mechanisms could be involved in UVB-induced apoptosis. However, the protease inhibitors zFA-fmk, CA-074-Me and ALLN all failed to prevent UVB-induced apoptosis in HeLa cells and keratinocytes. In conclusion, the protective effect of zVAD-fmk at high concentrations indicates that other proteases than caspases are active in the execution of UVB-induced apoptosis but further studies are needed to identify these proteases.