Contrasting effects of an ultraviolet B and an ultraviolet A tanning lamp on interleukin-6, tumour necrosis factor-α and intercellular adhesion molecule-1 expression

BACKGROUND: Recent studies have demonstrated that a tanning lamp emitting predominantly ultraviolet (UV) A induces significant yields of the type of potentially mutagenic DNA damage that are associated with the onset of skin cancer (i.e. cyclobutane pyrimidine dimers). UV-induced immunosuppression is also an important event leading to skin cancer. OBJECTIVES: To the modulation of key immunological molecules following exposure to a broad-spectrum UVB lamp and a predominantly UVA-emitting tanning lamp using model in vitro systems. METHODS: We compared secretion and mRNA expression of interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha in normal human epidermal keratinocytes, and interferon (IFN)-gamma-induced intracellular adhesion molecule (ICAM)-1 in normal human fibroblasts irradiated in vitro with a broad-spectrum UVB lamp or with a Philips 'Performance' tanning lamp. RESULTS: With broad-spectrum UVB irradiation, upregulation of IL-6 and TNF-alpha mRNA was detected 6 h after irradiation, and a dose-dependent increase of cytokines in the supernatants of irradiated cells was found 24 h after irradiation. In contrast, there was no cytokine secretion and little evidence for mRNA upregulation following exposure to a tanning lamp. When cells were exposed first to broad-spectrum UVB, then the tanning lamp, UVB-induced cytokine secretion was inhibited, although mRNA levels were upregulated to a level close to that observed with UVB alone. By using a Schott WG 320 nm filter to attenuate the level of UVB relative to UVA emitted by the tanning lamp, the inhibition of cytokine secretion was shown to be associated with UVA exposure. Both UV sources inhibited IFN-gamma-induced ICAM-1 mRNA expression in a dose-dependent fashion. By using a Schott WG 335 nm filter, inhibition of ICAM-1 mRNA expression by the tanning lamp was shown to be associated with UVB exposure. CONCLUSIONS: These results suggest that UV sources emitting different levels of UVA and UVB have differential effects on the modulation of different immunoregulatory molecules, and indicate that there are potential interactions between these wavelengths.     

Ultraviolet A and B affect human melanocytes and keratinocytes differently. A study of oxidative alterations and apoptosis

Ultraviolet (UV) radiation is an etiologic agent for malignant melanoma and non-melanoma skin cancer, but the spectral range responsible for tumor induction is still to be elucidated. In this study, we compared effects of UVA and UVB irradiation on normal human melanocytes (MCs) and keratinocytes (KCs) in vitro. We demonstrate that UVA irradiation induces immediate loss of reduced glutathione (GSH) in both MCs and KCs. Exposure to UVA also causes reduced plasma membrane stability, in both cell types, as estimated by fluorescein diacetate retention and flow cytometry. Furthermore, we noted reduction in proliferation and higher apoptosis frequency 24 h after UVA irradiation. UVB irradiation of KCs caused instant reduction of reduced GSH and impaired plasma membrane stability. We also found decline in proliferation and increased apoptosis after 24 h. In MCs, on the other hand, UVB had no effect on GSH level or plasma membrane stability, although increased apoptotic cell death and reduced proliferation was detected. In summary, MCs and KCs showed similar response towards UVA, while UVB had more pronounced effects on KCs as compared to MCs. These results might have implications for the induction of malignant melanoma and non-melanoma skin cancer.     

Direct effects on proliferation,antigen expression and melanin synthesis of cultured normal human melanocytes in response to UVB and UVA light

BACKGROUND/PURPOSE: Ultraviolet (UV) radiation; induces a variety of responses in the skin, including tanning and inflammation, and may also act as a carcinogen. As epidermal melanocytes are seen as the major targets of UV light, the present study was conducted to evaluate the direct effects of UVA and UVB irradiation on melanocytes in vitro. METHODS: Normal human epidermal melanocytes (NHM) were exposed on 3 consecutive days to UVA (0.072-7.2 J/cm2) and UVB (7.2-48 mJ/cm2), respectively, and changes of morphology, cell number, melanin synthesis and antigen expression (APAAP technique) were determined 5 days after the first exposure. RESULTS: UVA radiation caused only minimal effects on NHM by slightly inducing expression of the activation marker HMB-45 and decreasing expression of the proliferation marker Ki-67. No changes of morphology, cell number or melanin synthesis were detectable with any of the applied doses. On the other hand, UVB radiation significantly induced dendrite formation and decreased the number of NHM in a dose-dependent manner (74% of the controls at 7.2 mJ/cm2, 64% at 14.4 mJ/cm2 and 28% at 36 mJ/cm2). Significant induction of the activation marker HMB-45 was found in parallel to decreased expression of the differentiation marker K.1.2.58. UVB doses >or=9.6 mJ/cm2 also resulted in significant downregulation of the proliferation marker Ki-67, confirming the data of the cell counts, and melanin content was increased in NHM (20% over the controls, P<0.01) after applying 7.2 mJ/cm2 UVB. CONCLUSION: Our results may suggest that the effect of UVB radiation in skin is due to direct activation of melanocytes, whereas skin tanning caused by UVA is mediated rather in an indirect way.     

Expression and modulation of apoptosis regulatory molecules in human melanocytes: significance in vitiligo

Although the aetiology of the hypopigmentary disorder vitiligo is ill understood, it is clear that pigment producing cells are absent from vitiliginous lesional skin. The present study was designed to investigate the possible role of melanocyte-expressed apoptosis regulatory molecules in melanocyte disappearance. Flow cytometric evaluation of p53, p21, Bcl-2 and Bax revealed no differences in in vitro expression levels between normal control and non-lesional melanocytes. Moreover, no in situ immunohistological differences were observed in melanocytes present in control, non-lesional and perilesional skin. However, an enhanced number of p53+ nuclei, in the absence of detectable p21 expression, was detected in involved areas. The observed p53 expression pattern did not involve melanocytes and could be the result of ultraviolet (UV) A irradiation. Further, we showed that UVB is capable of modulating melanocyte-expressed apoptosis regulatory molecules. Consequently, a lethal dose of UVB was given to two groups of cultured normal control and non-lesional melanocytes. No significant differences were found when comparing the percentages and kinetics of UVB-induced apoptosis in these groups. In conclusion, our results indicate that the relative apoptosis susceptibility of melanocytes in vitiligo is comparable with that of normal control cells. It is therefore unlikely that vitiligo is causally related to dysregulation of apoptosis regulatory molecules.     

Attachment and chemotaxis of melanocytes after ultraviolet irradiation in vitro

Because ultraviolet (UV) radiation is able to influence the spatial distribution of melanocytes in melanocytic naevi in vivo, we investigated the influence of UV radiation on the ability of melanocytes to adhere to the extracellular matrix proteins fibronectin, laminin and collagen type IV in vitro. In addition, chemotaxis of melanocytes was studied using both fibronectin and the supernatants from irradiated, as well as non-irradiated, keratinocytes and fibroblasts as attractants. Melanocyte attachment to fibronectin was significantly increased 48 h after a single UV irradiation at 30 mJ/cm2 in comparison with that of non-irradiated melanocytes, whereas attachment to laminin and collagen type IV showed only minor changes after UV exposure. The UV-induced increase in attachment to fibronectin was suppressed by preincubation with antibodies against alpha5beta1 or alphavbeta3 integrin. Both immunohistochemistry and flow cytometric analysis showed an increase in alpha5beta1 integrin expression on melanocytes after UV exposure. The chemotaxis of melanocytes to fibronectin was not influenced by UV exposure. A decreasing migration rate of melanocytes towards the supernatants of UVA-irradiated fibroblasts was observed with increasing UVA doses. The chemotactic effects of conditioned medium of keratinocytes towards melanocytes was not influenced either by UVB or by UVA. The results indicate that UV radiation may alter the ability of melanocytes to adhere to certain substrates by modification of integrin expression. Because fibronectin, as the major target protein of UV-altered attachment, is located in the dermis, the UV-induced morphological changes in melanocytic lesions, with an increase in suprabasally located melanocytes within the epidermis, may be due to other changes in the adhesive properties of melanocytes.     

Responses of the 27-kDa heat shock protein to UVB irradiation in human epidermal melanocytes

Abstract:  Solar ultraviolet radiation (UVR) is a major environmental hazard for the skin, and UVB (280–320 nm) has been proposed to be a main factor for melanoma development. In response to sunlight exposure, the skin has adapted a number of innate resistance mechanisms. Among them is the small heat shock protein of 27 kDa (HSP27) known to play a role in the protection of cells from variety of environmental insults including UV irradiation. In this study, we demonstrated that UVB irradiation of cultured normal epidermal melanocytes initiates changes in HSP27 phosphorylation and localization. In unstressed melanocytes, HSP27 was present as the non-phosphorylated isoform. UVB irradiation with a physiological dose (7–25 mJ/cm²) resulted in the formation of a mono-phosphorylated isoform and sometimes a bi-phosphorylated isoform. The UVB-induced HSP27 phosphorylation was inhibited when melanocytes were treated with the antioxidant N -acetyl cysteine or inhibitor of p38 MAP kinase prior to UVB exposure, suggesting that UVB induced HSP27 phosphorylation through reactive oxygen species/p38 MAP kinase pathway. In response to UBV irradiation, HSP27 in melanocytes translocated from the cytoplasm to the nucleus. The HSP27 responses may provide some protective role against UVB-induced cell damage in the skin.     

Increased expression of Fas on human epidermal cells after in vivo exposure to single-dose ultraviolet (UV) B or long-wave UVA radiation

BACKGROUND: Apoptosis has been proposed to act as an important mechanism for eliminating keratinocytes that have been irreversibly damaged by ultraviolet (UV) irradiation. One way to induce apoptosis in keratinocytes is through activation of the cell surface receptor Fas (CD95), either with the ligand (FasL) or directly with UV radiation. OBJECTIVES: To investigate the regulation of Fas and FasL expression in human skin and the formation of apoptotic cells after in vivo exposure to UVB or long-wave UVA radiation. METHODS: Volunteers were irradiated with either 3 minimal erythema doses (MED) of UVB (n = 6) or 3 MED of long-wave UVA (n = 6) on buttock skin 12, 24 and 72 h before skin punch biopsies were taken. Expression of Fas and FasL was demonstrated by immunohistochemistry on cryostat sections. Apoptosis was assessed by the terminal deoxynucleotidyl transferase-mediated fluorescein-deoxyuridine triphosphate nick-end labelling reaction. RESULTS: In five of six subjects, exposure to UVB radiation resulted in increased homogeneous expression of Fas on epidermal cells, with greatest expression at 24 and 72 h after irradiation. In all subjects, exposure to long-wave UVA resulted in increased homogeneous expression of Fas on epidermal cells, with greatest expression at 12 h after irradiation. In five of six subjects, exposure to UVB radiation resulted in temporarily decreased expression of FasL, but after 72 h the expression of FasL had returned to the preirradiation level. The expression of FasL on epidermal cells after exposure to long-wave UVA showed considerable variation. UVB irradiation was a stronger inducer of epidermal apoptosis than was UVA irradiation. The number of apoptotic epidermal cells did not correlate with expression of Fas or FasL. CONCLUSIONS: In human skin the expression of Fas on epidermal cells increases after in vivo exposure to UVB or long-wave UVA. Exposure to UVB causes a temporary decrease in the expression of FasL on epidermal cells.     

Topical riboflavin attenuates ultraviolet B‐ and ultraviolet A‐induced immunosuppression in humans

Background: Riboflavin (vitamin B₂) plays a key role in cellular energy metabolism. We have observed previously that nicotinamide (vitamin B₃), which is also centrally involved in cellular energy restoration after UV irradiation, is highly immune protective in humans. We thus hypothesized that riboflavin might also confer immune protection. Methods: We irradiated healthy, nickel‐allergic volunteers with narrowband UVA (385 nm) and UVB (300 nm) at separate sites on the lower back. These areas were treated with riboflavin solution or vehicle at 24 h and again at 30 min before UV exposure. Forty‐eight hours after irradiation, volunteers were patch tested with nickel‐containing Finn chambers, at both irradiated and nonirradiated sites, with and without prior riboflavin treatment. The resulting contact hypersensitivity reactions at each site were then measured 72 h later with a reflectance erythema meter in order to determine and compare the immune suppressive effects of each intervention. Results: We observed that low doses of both UVB and longwave UVA1 were immune suppressive in humans. Topical riboflavin conferred immune protection against both wavebands. Conclusions: Riboflavin is immune protective in humans, and this may reflect the role of the B group vitamins in cellular energy restoration after UV exposure.     

UVA1 impairs the repair of UVB‐induced DNA damage in normal human melanocytes

The exact correlation between melanoma and sun‐light is still a controversially debated issue. Although natural sunlight contains various ratios of UVA and UVB, most investigators so far focused on the effects of single solar wavebands and neglected possible interactions. Therefore, in this study primary human melanocytes of three donors were simultaneously exposed to physiologic doses of UVA1 and UVB. Effects on apoptosis were analysed using annexin V assays and cell death ELISAs, and effects on DNA damage were investigated using southwestern slot blots. While UVA1 did not influence UVB‐induced apoptosis, UVA1 impaired the repair of UVB‐induced cyclobutane pyrimidine dimers (CPD) as the amount of CPD was 1.8 times higher in UVA1 + UVB than in UVB only exposed melanocytes six hours after irradiation. We conclude that UVA1 might contribute to melanomagenesis as it partially inhibits the repair of UVB‐induced CPD in human melanocytes while it does not affect UVB‐mediated apoptosis.     

Effects of UV radiation on the ultrastructure of human common pigmented naevi and lentigines.

In order to investigate how sunlight may affect naevi and lentigines, their melanocytes and the basement membrane, three irradiation protocols were applied directly to ten naevi and five lentigines on 2 subjects. Neither volunteer had sufficient naevi and lentigines to be able to use the three irradiation protocols on each of the subjects. Skin biopsies were fixed in glutaraldehyde followed by osmium tetroxide, thin-sectioned and examined in a Hitachi H-7000 transmission electron microscope. Following 14 consecutive single exposures of 3 MED of UVB or single exposures followed by 25 J/cm2 of UVA, 350 J/cm2 UVA with either 2040 or 2280 mJ/cm2 UVB, the basement membrane maintained its continuity. Melanocytes were not observed on the dermal side of the epidermal-dermal junction. UVA irradiation stimulated reinforcement of the basement membrane zone by collagen fibers. Centrioles found in melanocytes following irradiation suggest that these melanocytes maybe undergoing mitosis. Dermal fibroblasts were found to contain comparatively large quantities of melanin pigment. The pigment contained in these fibroblasts may in fact constitute an additional barrier against UV irradiation.     

紫外线照射后生成的微囊泡对成纤维细胞氧化损伤及凋亡的作用

目的：明确对UVA及UVB照射后皮肤成纤维细胞生成的微囊泡对成纤维细胞氧化损伤及凋亡的作用。方法：紫外线照射人皮肤成纤维细胞,提取细胞上清液中的微囊泡,利用光散射分析技术鉴定分析微囊泡的大小及数量。将紫外线照射后生成的微囊泡与正常成纤维细胞共孵育,荧光酶标仪定量检测活性氧含量,流式细胞仪检测细胞凋亡率。结果：UVA及UVB照射后皮肤成纤维细胞释放的微囊泡数量及大小明显高于正常成纤维细胞释放的微囊泡。正常纤维细胞、UVA和UVB照射后的成纤维细胞与微囊泡共孵育后活性氧荧光值分别为（52.76±1.4347）、（82.60±4.082）和（85.94±6.264）,凋亡率分别为（3.260±1.732）%,（28.94±2.430）%和（34.48±2.718）%,细胞的氧化损伤和凋亡可被抗氧化剂逆转。结论：急性中长波紫外线照射可诱导皮肤成纤维细胞释放微囊泡进一步介导细胞的氧化损伤和凋亡。     

黄芩甙对紫外线诱导人正常黑素细胞黑素合成的抑制作用研究

体外培养黑素细胞（MC）分别经隔日长波紫外线（UVA）或中波紫外线（UVB）照射和（或）黄芩处理后，观察细胞增殖情况，测定酪氨酸酶活性和黑素含量。结果：（1）UVA使细胞增殖增快，但剂量较大时增殖减发电量；UVB使细胞增殖减慢。二者均可使细胞酪氨酸酶活性和黑素含量高于对照组。（2）黄芩具有抑制UVA和UVB诱导的MC增殖、酪氨酸酶活性及黑素合成改变的作用。提示黄芩能抑制UVA和UVB诱导的细胞反应，还可通过抑制酪氨酸酶减少MC黑素合成。     

FK506 inhibits tumour necrosis factor-alpha secretion in human keratinocytes via regulation of nuclear factor-kappaB

BACKGROUND: Tacrolimus (FK506) ointment has been used for treatment of inflammatory dermatoses with remarkable success. Our previous studies have indicated that direct modulation of tacrolimus on keratinocytes (KCs) may have an impact on its therapeutic effect. The use of monoclonal antibody specific for tumour necrosis factor (TNF)-alpha has shown efficacy in treating both psoriasis and Crohn disease. Topical tacrolimus has also been shown to be effective for treating cutaneous manifestations of both diseases. OBJECTIVES: To explore the effects of FK506 on human KCs in terms of TNF-alpha secretion and to investigate the regulatory pathway involved. METHODS: Ultraviolet (UV) B-irradiated cultured KCs were treated with various concentrations of FK506. At indicated time points after UVB irradiation we determined: (i) the TNF-alpha concentrations present in the culture supernatants; (ii) the activation and translocation of nuclear factor (NF)-kappaB in the cell nucleus; and (iii) the protein expressions of IkappaB kinase (IKK) and IkappaB in the cell lysates. In addition, a mouse model was used to corroborate our in vitro findings in vivo. More specifically, topical tacrolimus was applied on to mouse skin unilaterally after UVB irradiation. The effects of FK506 on nuclear NF-kappaB expression of UVB-irradiated mouse skin were determined. RESULTS: Our results showed that FK506 dose-dependently downregulated the secretion of TNF-alpha from UVB-irradiated KCs. The activation and translocation of NF-kappaB in UVB-irradiated KCs were also dose-dependently suppressed by FK506. The degradation of IkappaB induced by UVB was also inhibited by FK506, while no change in IKK expression was noted regardless of UVB and FK506 treatment. Murine skin biopsies showed that nuclear NF-kappaB expression induced by UVB was inhibited by topical tacrolimus treatment. CONCLUSIONS: Our results indicate that FK506 inhibits TNF-alpha secretion in human KCs via direct regulation of NF-kappaB. This modulatory effect of FK506 on KCs offers a possible mechanism for how topical tacrolimus regulates cutaneous inflammatory conditions.     

Effect of ultraviolet (UV) A, UVB or ionizing radiation on the cell cycle of human melanoma cells

BACKGROUND: One important component of the cellular response to irradiation is the activation of cell cycle checkpoints. It is known that both ultraviolet (UV) radiation and ionizing radiation (IR) can activate checkpoints at transitions from G(1) to S phase, from G(2) phase to mitosis and during DNA replication. OBJECTIVES: To evaluate the effects of irradiation with different wavelengths on cell cycle alterations. METHODS: p53-deficient IPC-298 melanoma cells were irradiated with 10 J cm(-2) UVA, 40 mJ cm(-2) UVB, or with 7.5 Gy IR. Cell cycle effects were then determined by DNA/5-bromodeoxyuridine dual-parameter flow cytometry. RESULTS: IPC-298 cells irradiated in G(1) with UVA were not arrested at the G(1)/S transition, but at the G(2)/M transition. Despite p53 deficiency, the cells showed a G(1) arrest after UVB exposure. Furthermore, IR did not affect G(1) or S phase, but induced G(2) phase arrest. Hence, the effects of UVA, but not of UVB, on the cell cycle in p53-deficient melanoma cells are comparable with those of IR. CONCLUSIONS: UVA and IR induce radical-mediated strand breaks and DNA lesions, and UVB essentially induces thymine dimers that lead to excision repair-related strand breaks. Different cell cycle effects may be a consequence of different types of DNA damage. The results showed that UVB-irradiated p53-deficient cells are arrested in G(1). Irradiation with the solar radiation component UVB can therefore result in a beneficial retardation of tumour promotion in human skin carrying p53-mutated cell clones.     

紫外线诱导成纤维细胞凋亡及防护机制的初步探讨

目的 探讨紫外线诱导真皮成纤维细胞凋亡的发生机理以及绿茶多酚的主要成分表没食子儿茶素没食子酸酯(EGCG)对凋亡的保护作用。方法 用流式细胞仪及RT-PCR方法分别检测了成纤维细胞凋亡率变化以及凋亡相关基因Fas和Bcl-2 mRNA表达变化。结果 经中波紫外线(UVB)和长波紫外线(UVA)辐射的成纤维细胞,均在G1期前出现明显的亚二倍体(凋亡峰),凋亡率分别为34.79±2.24和29.69±3.05;而应用EGCG后凋亡率均明显下降为4.23±0.03和5.23±0.01。经统计学分析,差异有显著性(P<0.001)。Fas的mRNA表达在UVB及UVA辐射组均有较明显增加,分别为0.72±0.05和0.68±0.02;应用EGCG后,两组表达均明显减弱为0.35±0.02和0.47±0.03。经统计学分析,差异有显著性(P<0.001)。Bcl-2的mRNA经UVB辐射后,没有明显变化,仍有较强表达;而经UVA辐射以后,其mRNA表达明显减弱。为0.27±0.03,应用EGCG后,表达则又明显增强为0.51±0.04。结论 EGCG对UVB及UVA诱导的凋亡均有保护作用,但凋亡的发生机理以及保护机理则有所差异。     

Cumulative UV radiation dose and outcome in clinical practice: effectiveness of trioxsalen bath PUVA with minimal UVA exposure

BACKGROUND: The cumulative artificial ultraviolet (UV) exposure dose of dermatological patients was prospectively monitored in clinical conditions for a total of 2 years (August 1997 - July 1999). We focused on whole body UV treatments, i.e. the trioxsalen (TMP) bath PUVA, the broad-band UVB, and the UVA plus UVB phototherapy. METHODS: Irradiance of the UV devices was calibrated with a spectroradiometer. The cumulative UV doses received by the patients were recorded. A visual analog scale scoring system (VAS) was employed to assess the improvement of various skin conditions at the end of the treatment course. RESULTS: The analysis included 265 patients (141 females and 124 males) and a total of 311 UV treatment courses. Treatments consisted of 86 courses of TMP bath PUVA for psoriasis with a mean cumulative UVA dose of 3.54 J/cm2 and an improvement rate of 89%. For other conditions, 30 courses were needed, with a cumulative UVA dose of 1.47 J/cm2 and an improvement rate of 76%. Altogether, 47 UVB courses were undertaken for psoriasis, and the mean cumulative unweighted UV dose was 2.20 J/cm2, equivalent to 85 standard erythema doses (SED), and an improvement rate of 85%. A total of 25 UVB courses was used for other skin conditions with a mean UV dose of 1.05 J/ cm2, equivalent to 40 SED, and an improvement rate of 71%. A total of 123 courses of UVA plus UVB phototherapy were completed, resulting in a mean cumulative dose of 73.01 J/cm2 for UVA and 0.75 J/cm2 for the unweighted UVB, equivalent to 29 SED. The VAS improvement rate was 85%. CONCLUSION: The exceptionally low mean cumulative UVA dose in the TMP bath PUVA, taken together with the previous report showing no increase in the risk of squamous cell carcinoma or cutaneous malignant melanoma after TMP bath PUVA, suggests that TMP bath PUVA is an effective and safe therapeutic option.     

低剂量长波紫外线诱导培养的人皮肤黑素细胞适应性反应观察

目的 探讨低剂量长波紫外线(UVA)诱导培养人皮肤黑素细胞适应性反应的程度及特点。方法 以具有致死作用的86.4J/cm²UVA照射经7.2J/cm²低剂量UVA单次或多次预照射的培养人皮肤黑素细胞.光镜、电镜观察细胞形态学变化,流式细胞仪检测细胞凋亡的比例,单细胞凝胶电泳检测DNA损伤的程度。结果 单次或多次7.2J/cm²UVA预照射处理后的培养皮肤黑素细胞使随后86.4J/cm²UVA照射诱导的形态学上的毒性反应减轻,细胞凋亡的比例下降,DNA链断裂减少及修复加快,与未经预处理86.4J/cm²UVA照射的相应细胞比较差异有统计学意义(P<0.01或P<0.05);单次7.2J/cm²UVA预照射诱导培养皮肤黑素细胞的适应性反应在预照射12h后消失,而当低剂量UVA预照射的累积剂量达到28.8J/cm²以上时,预照射的培养细胞即使是14d后对86.4J/cm²UVA照射仍有明显的防护作用。结论 低剂量UVA照射可诱导培养的皮肤黑素细胞出现对随后高剂量UVA照射的适应性反应,其效应滞留期及强度与低剂量UVA的累积剂量有关。     

姜黄素对紫外线诱导损伤的HaCaT细胞的保护作用

目的比较姜黄素对UVA、UVB急性损伤的HaCaT细胞的保护作用。方法体外培养人永生化角质形成细胞株HaCaT细胞,UVA、UVB照射建立HaCaT细胞急性光损伤模型。姜黄素与HaCaT细胞共培养24 h后,MTT法检测细胞增殖能力,流式细胞仪检测细胞凋亡情况,确定无毒性姜黄素浓度。通过MTT法、流式细胞术分别检测添加姜黄素前后,UVA、UVB照射引起的HaCaT细胞损伤情况及胞内活性氧(Reactive oxygen species,ROS)水平变化。结果姜黄素浓度在5μmol/L以下时,正常细胞的增殖和凋亡不受影响。添加姜黄素前,UVA照射引起细胞增殖抑制、凋亡增加(P0.05),ROS增高67.9%;UVB照射引起细胞增殖抑制、凋亡增加(P0.05),ROS增高67.2%。添加姜黄素后,UVA、UVB组细胞损伤均减轻(P0.05),ROS水平升幅均下降,呈浓度依赖型。结论对于不同波长的紫外线诱导损伤的HaCaT细胞,姜黄素均可降低急性光损伤引起ROS水平升幅,具有抗氧化保护作用,其保护强度无差异,并且呈浓度依耐性。