慢性镉暴露对背角无齿蚌肝脏的氧化损伤效应

目的:探明氯化镉(CdCl2)暴露对背角无齿蚌肝脏中抗氧化酶活力及脂质过氧化的影响。方法:根据背角无齿蚌96 h镉离子(Cd²⁺)半致死剂量设置1个对照组和2个处理组(0.1和0.5 mg/L),分别检测镉暴露4周及镉清除4周期间背角无齿蚌肝脏中抗氧化酶[超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GPx)、过氧化氢酶(CAT)]的活力和脂质过氧化物丙二醛(MDA)的含量。结果:不同浓度Cd²⁺暴露对背角无齿蚌抗氧化酶活力及脂质过氧化产生不同程度的影响,低浓度Cd²⁺暴露的毒性效应较弱,高浓度Cd²⁺暴露可显著抑制肝脏SOD活力,诱导GPx活力升高,在暴露后期显著抑制CAT活力,MDA含量随着暴露时间的延长而显著升高。结论:慢性Cd²⁺暴露可影响背角无齿蚌肝脏抗氧化酶活力,引起脂质过氧化损伤,且作用机制与急性毒性不同。     

镉对胎盘绒毛外滋养层HTR-8/SVneo细胞内抗氧化酶活性的影响

目的:探究氯化镉(CdCl_2)对胎盘绒毛外滋养层HTR-8/SVneo细胞内活性氧(ROS)水平和抗氧化酶活性的影响。方法:用不同浓度的CdCl_2(0、3、6、12μmol/L)处理HTR-8/SVneo细胞24 h,或者用12μmol/L CdCl_2处理HTR-8/SVneo细胞不同时间(0、6、12、24 h)后,CCK-8检测细胞活性;采用时间依赖模型,显微镜下观察细胞形态变化;流式细胞术检测细胞内ROS含量变化;试剂盒法检测细胞内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽过氧化物酶(GPx)活性及丙二醛(MDA)水平的变化;用12μmol/L CdCl_2与500μmol/L ROS清除剂NAC共处理HTR-8/SVneo细胞24 h,观察NAC对细胞的保护效应。结果:CdCl_2可以显著抑制HTR-8/SVneo细胞活性,且呈剂量和时间依赖性(P<0.01);随着CdCl_2处理时间的延长,HTR-8/SVneo细胞逐渐皱缩、变圆;细胞内ROS水平和MDA含量呈时间依赖性升高,而SOD、CAT和GPx活性呈时间依赖性降低;NAC可以显著抑制CdCl_2引起的ROS及MDA含量升高,缓解CdCl_2引起的形态损伤和抗氧化酶活性降低(P<0.05)。结论:镉可以引起HTR-8/SVneo细胞内ROS升高,并导致SOD、CAT、GPx活性降低和脂质过氧化。     

镉对尖紫蛤抗氧化酶活性及脂质过氧化的影响

为阐明镉(Cd2+)对尖紫蛤消化盲囊和鳃抗氧化酶的毒性影响程度,研究了不同浓度的Cd2+(0.005、0.05、0.5 mg/L)在不同暴露时间(24h、72h、120h)对尖紫蛤鳃和消化盲囊中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-PX)的活性以及丙二醛(MDA)含量的影响。结果表明,在Cd2+浓度为0.005 mg/L时,在整个实验期间Cd2+对消化盲囊和鳃内的SOD、CAT、GSH-PX活性并无显著影响。在Cd2+浓度为0.05 mg/L和0.5 mg/L时,SOD、CAT、GSH-PX在鳃和消化盲囊中的活性都呈现出明显的时间剂量依赖关系。在0.05 mg/L暴露时,鳃和消化盲囊中的SOD、CAT和GSH-PX的活性随时间逐渐增强,在72h时达到最大值,但在120h时略有降低。在0.5 mg/L暴露时,消化盲囊中SOD、CAT及鳃中CAT活性在24h时上升达到最大值,但鳃中SOD直到72h才达到最大值,并均在120h下降到最低,其中消化盲囊中SOD和CAT活性在120h低于对照组,这可能与消化盲囊对Cd2+的敏感性高于鳃有关。在0.5 mg/L暴露的鳃中,GSH-PX在24h、72h活性并不上升,在120h甚至低于正常水平,0.5 mg/L暴露的消化盲囊中,24h时迅速增高,然后逐渐下降到正常值。这可能与Cd2+结合了GSH-PX的活性中心,降低了GSH-PX的活性有关。与3种酶活性随着时间延长和剂量的增加,酶活性会降低的变化趋势不同,鳃和消化盲囊中的MDA的含量随时间延长和剂量的增加而增加,并不出现下降,这表明尖紫蛤鳃和消化盲囊中的MDA含量可以灵敏的反映机体内的氧化损伤程度,但不能敏感的反映水体中Cd2+的污染情况。     

全氟辛烷磺酰基化合物对剑尾鱼肝脏抗氧化物酶活性的影响

目的研究全氟辛烷磺酰基化合物(PFOS)暴露对剑尾鱼(Xiphophorus helleri Heckel)抗氧化物酶活性的影响,探讨PFOS对鱼类的致毒机理。方法使用浸润法以3.5、7.0、14.0和28.0 mg/L四个PFOS浓度为剑尾鱼染毒,定量测定了96 h内肝脏组织中的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-PX)活性及丙二醛(MDA)含量的变化。结果 PFOS暴露12 h后,除28.0 mg/L组SOD活性被显著性抑制外,其余各组与对照组均无显著性差异(P>0.05);7.0 mg/L组和14.0 mg/L组在24 h被极显著诱导(P<0.01),并且一直保持至96 h。CAT活性随PFOS浓度的升高而降低,12 h时,除3.5 mg/L组外,其余各组CAT活性被显著或极显著抑制,至24 h时,各组CAT活性有上升趋势,但48 h后,各组呈不断下降趋势持续至96 h,其CAT活性恢复到12 h水平。GSH-PX活性变化与CAT活性变化趋势相似,其中28.0 mg/L组在不同时间均被显著性抑制,并在96 h时抑制率达到最高值64.8%。MDA含量在12 h时呈小幅下降趋势,但随着暴露时间的延长,各处理组MDA含量呈连续上升趋势,并在96 h时达到最高点,诱导率分别为71.2%、70.1%和85.1%。结论结果表明,SOD的高活性是由于机体中超氧阴离子的存在,而高浓度的超氧阴离子能够灭活CAT和GSH-PX活性,因此,CAT和GSH-PX活性始终低于对照组。GSH-PX对PFOS的敏感性高于CAT。MDA含量持续升高反映出细胞组织已经遭受到氧化损伤。剑尾鱼活体的实验表明,PFOS能够诱导肝脏氧化应激反应,氧化损伤是PFOS致毒的主要途径之一。     

溴化1-己基-3-甲基咪唑对斜生栅藻抗氧化酶和膜脂过氧化的影响

研究了1、5、10、15、20 mg·L-1的离子液体溴化1-己基-3-甲基咪唑([C6mim]Br)在处理斜生栅藻24、48、96 h时对其抗氧化酶系统和膜脂过氧化的影响.结果表明:[C6 mim]Br处理24 h时,在各浓度水平均引起藻细胞可溶性蛋白和丙二醛(MDA)含量、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性的显著增高.48、96 h时,SOD 活性在各浓度水平均维持在较高水平,最大值出现在较低处理浓度下;其他指标有随着处理浓度增加而升高的趋势,且显著高于对照,但其数值多数比24 h时的有所下降.CAT活性与可溶性蛋白含量的变化趋势很相似,两者与MDA含量的变化趋势也较相似.[C6mim]Br造成了藻细胞的明显脂质过氧化反应,具有一定的环境毒性;抗氧化酶SOD和CAT可以作为[C6mim]Br胁迫分子水平上的敏感生物标志物.     

吡啶硫酮铜胁迫对凡纳滨对虾肝胰腺能量利用、脂质过氧化指标和基因表达的影响

目的 研究吡啶硫酮铜(Cu PT)对凡纳滨对虾Litopenaeus vannamei肝胰腺能量利用、脂质过氧化相关指标和抗氧化、凋亡相关基因表达量的影响。方法 设置空白对照组、DMSO溶剂对照组(0.128 m L·L^-1)和2个Cu PT处理组(64μg·L^-1和128μg·L^-1),每组3个平行,在200 L水体中暴露48 h,分别于胁迫0 h、3 h、12 h、24 h和48 h取肝胰腺进行测定。结果 随着Cu PT暴露浓度的增加及胁迫时间的延长,凡纳滨对虾肝胰腺中的糖原、乳酸含量显著下降(P<0.05),丙二醛含量显著升高(P<0.05);锰超氧化物歧化酶基因、谷胱甘肽过氧化物酶基因、过氧化氢酶基因和凋亡相关基因半胱氨酸蛋白酶3基因和肿瘤抑制基因的表达水平也发生了显著变化(P<0.05)。结论 CuPT可能影响凡纳滨对虾正常能量供应,并使机体出现脂质过氧化,还会影响机体内抗氧化应激以及凋亡相关基因的表达水平。     

DBP致雌性仔鼠卵巢的氧化应激及VC的干预作用

为探明邻苯二甲酸二丁酯(DBP)宫内暴露对雌性仔鼠卵巢脂质过氧化水平的影响及维生素C(Vit C)的抗氧化应激作用。本研究将20只Wistar孕鼠随机分为5组,分别为高(500 mg/kg)、低(100 mg/kg)剂量DBP染毒组以及高(500 mg/kg)、低(100 mg/kg)剂量DBP+Vit C(125 g/L)干预组和对照(玉米油)组,每组4只。自妊娠第1~19天,每天1次灌胃染毒DBP(10 m L/kg);采用自由饮水方式进食Vit C(约40 m L/d)。待雌性仔鼠出生21 d时,取其卵巢组织,称重,并测定MDA、GSH含量和GSH-Px、SOD、CAT活性。研究发现,与对照组相比,高、低剂量DBP染毒组MDA含量均明显升高,SOD、CAT、GSH-Px活性均明显降低(p0.05)。高、低剂量DBP+Vit C干预组的仔鼠卵巢组织中MDA含量与相同剂量DBP染毒组相比显著下降,GSH-Px、SOD、CAT活性显著升高(p0.05)。综上所述,DBP宫内暴露可致雌性仔鼠卵巢组织产生脂质过氧化反应,诱导氧化应激,造成潜在生殖毒性,抗氧化剂Vit C对于DBP所致生殖系统的氧化损伤具有一定的保护作用。这为进一步开展DBP生殖发育毒性的机制研究和预防干预提供理论依据。     

镉对长江华溪蟹精巢抗氧化酶活性及脂质过氧化的影响

在实验条件下,将健康性成熟雄性长江华溪蟹Sinopotamon yangtsekiense暴露于0、7.25、14.5、29、58和116 mg/L浓度的镉(Cd2+)溶液中,分别于1 d、3 d、5 d和7 d时测定精巢中超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氧酶(CAT)活性及脂质过氧化产物丙二醛(MDA)的含量.结果显示,不同时间段3种酶活性和MDA含量均具有浓度和时间效应关系,表明急性镉暴露对精巢有明显的毒性作用,其作用机制与抗氧化酶活力变化和脂质过氧化加剧有关.     

桂丁、草蔻挥发油抗氧化性研究

采用脂质过氧化方法和DPPH方法分别检测了2种植物挥发油抗脂质过氧化活性和清除自由基活性.且通过和阳性对照Vitamin E和Vitamin C的比较发现2种植物挥发油均有不同程度的抗脂质过氧化活性和清除自由基的活性.草蔻的抗脂质过氧化活性在低浓度下抑制率很高,在浓度为0.097～1.2 mg/mL之间其抗氧化能力强于桂丁.用IC50和EC50来评价抗脂质过氧化能力和清除自由基活性,则草蔻挥发油的抗脂质过氧化活性最强,且强于阳性对照Vitamin C,即草蔻的IC50为0.099 mg/mL.对于草蔻和桂丁的清除自由基的能力是相似的,EC50分别为4.50和4.46 mg/mL.     

慢性镉暴露对斑马鱼卵巢组织的氧化损伤和子代发育的母源影响

目的:采用半静态毒性实验方法,研究慢性镉暴露对性成熟斑马鱼卵巢组织抗氧化酶活性、脂质过氧化水平的影响及其母源传递毒性效应。方法:依据前期测定的96 h LC50,参考国家渔业标准,设置5个镉处理组(0.058、0.116、0.232、0.580、1.160 mg/L)和1个对照组,镉暴露21 d后,对卵巢组织超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)活性及脂质过氧化物丙二醛(MDA)含量进行测定,并对其受精率、F1代胚胎孵化率及96 hpf幼鱼体长进行统计分析。结果:不同浓度镉暴露均导致卵巢组织SOD、CAT和GPx活性显著降低、MDA含量显著升高并呈浓度依赖效应。子代母源毒性分析显示,与对照组相比,0.232和0.580 mg/L浓度组受精率均显著下降,0.232 mg/L浓度组F1代胚胎孵化率显著降低;各浓度组受精后96 h幼鱼体长与对照组相比有显著性差异,且随着镉浓度的增加体长显著变短。结论:慢性镉暴露导致斑马鱼卵巢组织抗氧化酶活性受到显著抑制,对组织和细胞造成严重氧化损伤,并通过母源传递导致子代发育的毒性效应。     

白藜芦醇对紫外线照射后人角质形成细胞AQP3 表达的影响

目的:探讨白藜芦醇对紫外线照射后人皮肤角质形成细胞水通道蛋白3(AQP3)表达的影响及意义。方法:原代培养人皮肤角质形成细胞,采用UVB(20mJ/cm2,40mJ/cm2)照射角质形成细胞后,立即加入0.1mmol/L的白藜芦醇进行干预。RT-PCR检测照射前后角质形成细胞中AQP3 mRNA的表达量,并用羟胺法、比色法、TBA法检测照射前后细胞超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活性及丙二醛(MDA)含量。结果:1.UVB照射后角质形成细胞AQP3 mRNA的表达量下降(P<0.05),且UVB照射剂量越大,AQP3 mRNA下降越显著(P<0.05)。2.白藜芦醇能显著增加UVB照射后角质形成细胞SOD和GSH-Px活性,并降低细胞MDA含量(P<0.05)。3.白藜芦醇能显著抑制UVB导致的角质形成细胞AQP3 mRNA下降(P<0.05)。结论:白藜芦醇可能通过抑制UVB导致的AQP3 mRNA下降,及提高氧化酶活性、清除自由基的功能,从而延缓皮肤衰老。     

The effect of local UVB skin irradiation on the rate of formazan deposition in the epidermis of hairless mice studied by means of a tetrazolium-reduction method

One-hundred-and-twenty hairless mice were irradiated with UVB (310 nm, exposure 60 mJ/cm2) on a limited area of the dorsal skin. At different time intervals after irradiation, the rate of endogenous dehydrogenase activity per mg dry epidermis was measured by the tetrazolium reduction method. The amount of formazan deposited remained normal for 18 h, and then increased, reaching a peak significantly higher than normal at 24 h, and thereafter returned to normal. At day 8 there was a new, probably significant peak. The reaction was followed for 14 days. It was concluded that UVB irradiation provokes a period of increased formazan deposition in the epidermis, similar to what has been observed after ionizing radiation and chemical carcinogens. The validity of the tetrazolium test for skin carcinogenic irritaments was thus also confirmed.     

Protective effect of inositol hexaphosphate against UVB damage in HaCaT cells and skin carcinogenesis in SKH1 hairless mice

UVB radiation damages keratinocytes, potentially inducing chronic skin damage, cutaneous malignancy, and suppression of the immune system. Naturally occurring agents have been considered for prevention and treatment of various kinds of cancer, including skin cancer. Inositol hexaphosphate (IP6), an antioxidant, is a naturally occurring polyphosphorylated carbohydrate that has shown a strong anticancer activity in several experimental models. We assessed the protective effects of IP6 against UVB irradiationinduced injury and photocarcinogenesis by using HaCaT cells (human immortalized keratinocytes) and SKH1 hairless mice. We found that IP6 counteracts the harmful effects of UVB irradiation and increases the viability and survival of UVB-exposed cells. Treatment with IP6 after UVB irradiation (30 mJ/cm(2)) arrested cells in the G(1) and G(2) M phases while decreasing the S phase of the cell cycle. Treatment with IP6 also decreased UVB-induced apoptosis and caspase 3 activation. Topical application of IP6 followed by exposure to UVB irradiation in SKH1 hairless mice decreased tumor incidence and multiplicity as compared with control mice. Our results suggest that IP6 protects HaCaT cells from UVB-induced apoptosis and mice from UVB-induced tumors.     

Changes in lipid peroxide levels and activity of reactive oxygen scavenging enzymes in skin, serum and liver following UVB irradiation in mice.

The effect of acute UVB on the generation of reactive oxygen species (ROS) in the skin and the induction of ROS scavenging enzymes in situ was examined. Lipid peroxide levels and the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px) and D-glucose-6-phosphate dehydrogenase (G-6-P-D) were determined in the skin, serum, and liver of ICR mice subjected to 1400 mJ/cm2 of acute UVB irradiation. In irradiated skin, lipid peroxides were increased at 3 and 24 hr after irradiation, whereas the four ROS scavenging enzymes were generally decreased during the first 48 hr after irradiation. In the serum, lipid peroxides showed an increase at 3 hr, but enzyme activities remained negligible. In the liver, lipid peroxides showed similar behaviour to that in skin. GSH-Px activity in the liver was decreased during the first 24 hr, whereas G-6-P-D showed substantial fluctuation and SOD and catalase activities showed no change. These data are consistent with a model in which lipid peroxides generated in the UVB-irradiated lesions are transported to the liver and there metabolized by the scavenging enzymes induced in situ.     

Photoprotection by antioxidants against UVB-radiation-induced damage in pig skin organ culture

Topically applied antioxidants constitute an important group of protective agents against skin damage induced by ultraviolet radiation. The current study was performed to investigate whether a recently developed ex vivo pig skin model was suitable for short-term studies of the mechanism(s) of UVB-radiation-induced skin damage; the protective effect of topical application of alpha-tocopherol, l-ascorbic acid, alpha-lipoic acid, glutathione ethylester and N-acetylcysteine was tested. Increasing doses of the antioxidants were applied topically on ex vivo pig skin explants and allowed to penetrate for 60 min. Epidermal antioxidant bioavailability was measured before and 60 min after exposure to an ultraviolet B (UVB) radiation of 7.5 kJ/m2. Cell viability (trypan blue dye exclusion) and apoptosis were measured 48 h later in isolated keratinocytes. UVB-radiation-induced epidermal lipid peroxidation was determined immediately after exposure of the skin to a UVB dose of 28 kJ/m2. All antioxidants tested became bioavailable in pig skin epidermis, and none of them were depleted after UVB-radiation exposure. Increasing doses of the antioxidants tested decreased UVB-radiation-induced cell death and apoptosis. The highest doses of antioxidants prevented UVB-radiation-induced lipid peroxidation; alpha-lipoic acid only tended to decrease lipid peroxidation. In conclusion, a single topical dose of the above antioxidants on ex vivo pig skin can reduce UVB-radiation-induced oxidative stress and lipid peroxidation and thereby reduce apoptotic stimuli and cell death. Furthermore, the ex vivo pig skin model was a useful tool for testing compounds for their antioxidant activity.     

Marked expression of glutathione S-transferase A4-4 detoxifying 4-hydroxy-2(E)-nonenal in the skin of rats irradiated by ultraviolet B-band light (UVB).

Enzyme, Western blot, and immunohistochemical analyses indicated that rat skin cytosol contained no detectable level of the homodimeric, alpha-class glutathione S-transferase (rGST) A4-4 which catalyzes the GSH conjugation of the toxic product, 4-hydroxy-2(E)-nonenal (HNE), nonenzymatically formed from n-6 polyunsaturated fatty acid residues of lipids by lipid peroxidation. Rats irradiated by single doses (4000-24,000 mJ/cm(2)) of ultraviolet B-band light (UVB, 200 mJ/cm(2)/min) markedly expressed rGSTA4-4 in the skin at a level one-fifth that of the liver in apparent specific activity toward HNE at a single dose of 24,000 mJ/cm(2). Skin rGSTA4-4 was isolated, purified to homogeneity, and identified with hepatic rGSTA4-4 by reverse-phase partition HPLC and by amino acid sequence analysis of its CNBr fission peptides. Immunohistochemistry with polyclonal antibody raised against rGSTA4-4 demonstrated the selective expression of rGSTA4-4 in epidermis and sebaceous glands localized in dermis after UVB irradiation.     

Repeated exposures of human skin equivalent to low doses of ultraviolet-B radiation lead to changes in cellular functions and accumulation of cyclobutane pyrimidine dimers.

Chronic exposure to sunlight may induce skin damage such as photoaging and photocarcinogenesis. These harmful effects are mostly caused by ultraviolet-B (UVB) rays. Yet, less is known about the contribution of low UVB doses to skin damage. The aim of this study was to determine the tissue changes induced by repeated exposure to a suberythemal dose of UVB radiation. Human keratinocytes in monolayer cultures and in skin equivalent were irradiated daily with 8 mJ/cm2 of UVB. Then structural, ultrastructural, and biochemical alterations were evaluated. The results show that exposure to UVB led to a generalized destabilization of the epidermis structure. In irradiated skin equivalents, keratinocytes displayed differentiated morphology and a reduced capacity to proliferate. Ultrastructural analysis revealed, not only unusual aggregation of intermediate filaments, but also disorganized desmosomes and larger mitochondria in basal cells. UVB irradiation also induced the secretion of metalloproteinase-9, which may be responsible for degradation of type IV collagen at the basement membrane. DNA damage analysis showed that both single and repeated exposure to UVB led to formation of (6-4) photoproducts and cyclobutane pyrimidine dimers. Although the (6-4) photoproducts were repaired within 24 h after irradiation, cyclobutane pyrimidine dimers accumulated over the course of the experiment. These studies demonstrate that, even at a suberythemal dose, repeated exposure to UVB causes significant functional and molecular damage to keratinocytes, which might eventually predispose to skin cancer.     

Distinct melanogenic response of human melanocytes in mono-culture, in co-culture with keratinocytes and in reconstructed epidermis, to UV exposure

Striking differences are observed in the melanogenic response of normal human melanocytes to UVA and UVB irradiation depending on culture conditions and the presence of keratinocytes. Exposure of melanocytes co-cultured with keratinocytes to UVB irradiation triggered, already at low doses (5 mJ/cm2), an increase in melanin synthesis whereas in melanocyte mono-cultures, UVB doses up to 50 mJ/cm2 had no melanogenic effect. Unlike UVB, UVA exposure caused the same melanogenic response in both mono- and co-cultures. Removing certain keratinocyte growth factors from the co-culture medium abolished the melanogenic response to UVB, but not to UVA exposure. When integrated into the basal layer of a reconstructed human epidermis, human melanocytes similarly reacted to UVA and UVB irradiation as in vivo by increasing their production and transfer of melanin to the neighboring keratinocytes which resulted in a noticeable tanning of the reconstructed epidermis. The presence of a dense stratum corneum, known to scatter and absorb UV light, is responsible for higher minimal UVB and UVA doses required to trigger a melanogenic response in the reconstructed epidermis compared to keratinocyte-melanocyte co-cultures. Furthermore, an immediate tanning response was observed in the pigmented epidermis following UVA irradiation. From these results we conclude that: (i) keratinocytes play an important role in mediating UVB-induced pigmentation, (ii) UVA-induced pigmentation is the result of a rather direct effect on melanocytes and (iii) reconstructed pigmented epidermis is the most appropriate model to study UV-induced pigmentation in vitro.     

Ultraviolet B(UVB)-induced cox-2 expression in murine skin: an immunohistochemical study

Cyclooxygenase (COX) is the rate-limiting enzyme in the production of prostaglandins from arachidonic acid. This enzyme exists in at least two isoforms, COX-1 and COX-2. COX-1 is constitutively expressed in most tissues and plays various physiological roles. However, COX-2 expression is induced by a variety of agents, which include pro-inflammatory agents and mitogens. Evidence exists to indicate that increased expression of COX-2 occurs in several types of epithelial neoplasms. In this study, we show the effect of chronic exposure of murine skin to carcinogenic UVB on cutaneous COX-2 expression. SKH-1 mice were irradiated with 180 mJ/cm(2) UVB daily for five days a week for periods ranging from 1 to 20 weeks. Nontumor bearing skin areas of irradiated mice, skin of age-matched controls and benign papillomas and malignant tumors were assessed immunohistochemically for COX-2 expression in these mice. No epidermal staining occurred in any of the non-UVB-treated controls throughout the experiment. Epidermal COX-2 expression only occurred in UVB-irradiated mice. After 1 and 5 weeks of irradiation, patchy epidermal staining mostly confined to the granular layer and stratum corneum was observed. At week 9, staining intensity had increased, particularly in the granular layer. At week 13, staining was uniformly seen in all epidermal layers with particular prominence in the basal cell layer underlying areas of visible epidermal hyperplasia. It is of interest that the most intense staining was seen in the perinuclear region of keratinocytes and at the plasma membrane. At week 20, COX-2 staining was predominant in the granular layer, although in some tissue sections, the entire epidermis was positive. In benign papillomas, staining was confined to the superficial layers of the epidermis and in squamous cell carcinomas (SCCs), patchy staining in the granular and spinous layers predominated. In general, COX-2 expression was more intense in well-differentiated SCCs than in papillomas. In summary, our results indicate that COX-2 serves as an early marker of epidermal UVB exposure and its expression increases in benign papillomas and in SCCs. These results suggest that pharmacological intervention using specific COX-2 inhibitors could have anticarcinogenic effects in UVB-induced human skin cancer.     

Up-Regulation and redistribution of Bax in ultraviolet B-irradiated melanocytes

Ultraviolet B (UVB) radiation may activate or deteriorate cultured human epidermal melanocytes, depending on the doses and culture conditions. It is also reported that cultured human epidermal melanocytes derived from different pigmentary phenotypes showed different responses to UVB radiation. In this study, we examined whether apoptosis of melanocytes can be induced by physiologic doses of UVB irradiation using cultured human epidermal melanocytes derived from oriental males of skin types III and IV. Propidium iodide staining for DNA condensation and flow cytometric analyses demonstrated the apoptotic cell death of melanocytes following UVB irradiation (0-30 mJ/cm2). The levels of p53, Bax, and Bcl-2, determined by immunoblotting, revealed a dose-dependent increase in p53 and Bax, but the level of Bcl-2 remained unchanged. Confocal microscopic examination showed that Bax moved from a diffuse to a punctate distribution after UVB irradiation. However, there were no changes in the pattern of distribution of Bcl-2. These data suggest that the high constitutional level of Bcl-2 may protect melanocytes from UVB-induced injury, and that apoptotic death of melanocytes may be induced by the elevation and redistribution of Bax.