mTOR-自噬通路对脓毒症小鼠海马小胶质细胞表型的影响

目的 探讨哺乳动物雷帕霉素靶蛋白（mTOR）-自噬通路对脓毒症小鼠海马小胶质细胞表型的影响。方法 54 只雄性 ICR 小鼠,按照随机数字表法分为 3 组（n=18）：假手术组（Sham 组）、脓毒症组（CLP 组）和脓毒症+mTOR抑制剂雷帕霉素组（CLP+Ra组）。Sham组只进行开腹手术操作;CLP组采用盲肠结扎穿孔术制备脓毒症小鼠模型;CLP+Ra 组于造模前 6 h腹腔注射雷帕霉素（1.5 mg/kg）。于造模后 24 h各组取 6只,采用酶联免疫吸附试验（ELISA）法检测海马组织肿瘤坏死因子（TNF）-α、白细胞介素（IL）-1β、IL-10和转化生长因子（TGF）-β水平;采用免疫荧光染色法检测海马组织切片离子钙接头蛋白分子（Iba）-1/CD86和 Iba-1/CD206阳性细胞数量;采用蛋白免疫印迹法测定海马组织 mTOR磷酸化（p-mTOR）水平、自噬相关蛋白微管相关蛋白 1轻链 3Ⅱ（LC3Ⅱ）和 Beclin-1表达情况。结果 与 Sham组比较,CLP组 TNF-α、IL-1β、IL-10和 TGF-β水平升高,Iba-1/CD86和 Iba-1/CD206阳性细胞数量增加,p-mTOR水平上调,LC3Ⅱ和 Beclin-1表达下调（均 P＜0.05）。与 CLP组比较,CLP+Ra组 TNF-α和 IL-1β水平降低,IL-10和 TGF-β水平升高,Iba-1/CD86阳性细胞数量减少,Iba-1/CD206阳性细胞数量增加,p-mTOR水平下调,LC3Ⅱ和 Beclin-1表达上调（均 P＜0.05）。结论 mTOR-自噬通路通过调节小胶质细胞表型转化,影响脓毒症小鼠海马炎症反应。     

细胞复制性衰老及过氧化氢诱导的早衰过程中基因组DNA甲基化水平改变

目的检测体外培养的人胚肺成纤维细胞复制性衰老及过氧化氢诱导的细胞早衰过程中基因组DNA甲基化及甲基转移酶DNMT1的表达改变。方法应用5-甲基胞嘧啶免疫荧光法及[3H]甲基掺入法检测细胞衰老不同阶段细胞基因组DNA整体甲基化变化趋势,以Q-PCR和Western Blot方法检测DNMT1的mRNA和蛋白表达变化。结果细胞复制性衰老过程及早衰过程中,与年轻细胞组相比,5-甲基胞嘧啶免疫荧光强度逐渐降低,[3H]甲基掺入实验结果显示,甲基化的CpG%分别为年轻细胞组68.2%,中年细胞组41.9%,复制性衰老组16.1%,而早衰起始组63.5%,早衰持续组18.0%。DNMT1的mRNA和蛋白表达水平一致,在细胞复制性衰老过程中,DNMT1表达呈下降趋势,复制性衰老细胞组表达水平最低,而早衰起始组DNMT1表达显著升高,早衰持续组又降低至同复制性衰老组水平。结论本试验条件下,在细胞复制性衰老及早衰过程中,基因组DNA甲基化水平逐渐降低,基因组低甲基化是衰老细胞的伴随状态,与DNMT1水平降低有关。     

N-甲基-N'-硝基-N-亚硝基胍对哈萨克族食管正常上皮细胞甲基转移酶表达及活性的影响

目的体外实验检测N-甲基-N'-硝基-N-亚硝基胍(MNNG)对哈萨克族食管正常上皮细胞DNA甲基转移酶的表达及活性改变,以此探讨亚硝胺类化合物致食管上皮组织发生恶变的表遗传机制。方法以0、0.75、1.50和3.00μg/ml MNNG处理哈萨克族正常食管上皮细胞24 h,采用高效液相色谱法(HPLC)和DNA甲基转移酶活性检测试剂盒检测细胞基因组DNA整体甲基化水平和DNA甲基转移酶活性的改变;并采用RT-PCR和Western Blot法检测DNA甲基转移酶mRNA及蛋白表达。结果 1.50和3.00μg/ml MNNG组与对照组比较细胞基因组DNA整体甲基化水平分别降低8.07%和17.58%,且各染毒组之间比较差异有统计学意义(F=60.342,P0.01);与对照组比较各染毒组DNMT1、DNMT3a、DNMT3b酶活性均升高,且与MNNG浓度呈正相关(r=0.967,P0.01;r=0.897,P0.01;r=0.716,P0.01);与对照组比较各染毒组DNMT1、DNMT3a、DNMT3b基因mRNA及蛋白表达水平均升高,且与MNNG浓度呈正相关(r=0.814,P0.05;r=0.732,P0.01;r=0.578,P0.05;r=0.944,P0.01;r=0.900,P0.01;r=0.887,P0.01)。结论 MNNG可致哈族正常食管上皮细胞基因组DNA整体甲基化水平下降,提高DNMT1、DNMT3a、DNMT3b表达及活性。     

抗氧化剂SS-31肽对脓毒症小鼠海马神经元凋亡与炎症反应的影响

目的：观察抗氧化剂 SS-31肽对脓毒症小鼠海马神经元凋亡与炎症反应的影响。方法：成年雄性 C57BL/6小鼠65只随机分为3组：假手术组（Sham 组,15只）、脓毒症组（CLP 组,25只）和脓毒症+SS-31肽组（SS-31肽组,25只）。 CLP 组和 SS-31肽组建立盲肠结扎穿孔模型。术毕 SS-31肽组腹腔注射 SS-31肽（5 mg·kg-1）,Sham 组和 CLP 组注射等容生理盐水,连续单次注射6天。记录术后7天内死亡率;随后处死小鼠取海马组织,检测线粒体活性氧自由基（ROS）水平,Western bloting 检测总细胞色素 C（Cyt C）、细胞质 Cyt C、caspase 3和 Nlrp 3含量;酶联免疫吸附法（ELISA）检测白细胞介素1β（IL-1β）和神经元特异性烯醇化酶（NSE）水平。结果：与CLP 组相比,SS-31肽组7天死亡率明显降低（52% vs 24%）,线粒体 ROS 水平、细胞质 Cyt C、caspase 3和 Nlrp 3含量以及 IL-1β、NSE 水平均减少（P<0.05）。结论：抗氧化剂 SS-31肽可降低脓毒症小鼠脑海马组织中线粒体 ROS 水平,抑制凋亡和炎症反应,改善损伤,降低死亡率。     

PI3K/AKT信号通路在大鼠腹腔感染性脓毒症急性肾损伤中的作用

目的 探究磷脂酰肌醇3-激酶/蛋白激酶B（PI3K/AKT）信号通路在大鼠腹腔感染性脓毒症急性肾损伤（acute kidney injury,AKI）中的作用。方法 使用盲肠结扎穿孔（cecal ligation and puncture,CLP）的方法制备大鼠腹腔感染性脓毒症模型,按照检测时间点（24、48、72 h）分组,于术后各时间点用全自动生化分析仪检测血清肌酐（Cr）、尿素氮（BUN）水平;用实时定量聚合酶链反应（Real-time PCR）检测大鼠肾脏组织PI3K mRNA及AKT mRNA的表达水平,采用蛋白免疫印迹法（Western blot,WB）检测大鼠肾脏组织Nod样受体蛋白3（NLRP3）、凋亡相关斑点样蛋白（ASC）、半胱氨酸天冬氨酸特异性蛋白酶1（Caspase-1）蛋白表达水平,采用酶联免疫吸附法（ELISA）检测血清肿瘤坏死因子-α（TNF-α）、白细胞介素（IL）-1β及IL-18的表达水平。假手术组除不进行盲肠结扎及穿孔外,其余操作与CLP组相同。结果 与假手术组相比,CLP各组大鼠血Cr、BUN水平出现明显升高（P＜0.05）,肾脏组织内PI3K及AKT mRNA 表达水平明显升高（P＜0.01）,且其下游 NLRP3 炎性小体蛋白表达水平明显升高（P＜0.01）,同时血清TNF-α、IL-1β及IL-18水平明显升高（P＜0.01）。结论 PI3K/AKT信号通路在腹腔感染性脓毒症AKI中具有重要作用,其活化诱导下游NLRP3炎性小体活化增加,进而使炎症因子释放增加并加重脓毒症病情。     

DNMT1通过下调SOX1表达参与宫颈癌生长和转移的机制研究

目的 探讨DNA甲基转移酶1（DNMT1）通过调节性别决定区Y-框1（SOX1）表达对宫颈癌（CC）生长和转 移的影响。方法 采用亚硫酸氢盐定量PCR测定CC组织和细胞及CC癌旁组织和正常宫颈细胞中SOX1甲基化水 平,Western blot检测DNMT1、SOX1蛋白表达。将HeLa229和SW756细胞分为DNMT1-NC组、DNMT1-siRNA组和空 白组,采用亚硫酸氢盐定量 PCR 测定 SOX1 甲基化比例,Western blot 检测 DNMT1、SOX1、c-Myc、Cyclin D1 及 β- catenin蛋白表达,细胞克隆和裸鼠成瘤实验测定细胞增殖,Transwell实验测定细胞迁移和侵袭。结果 CC组织较癌 旁组织DNMT1表达水平及SOX1甲基化比例增高,SOX1蛋白表达降低（P＜0.05）;宫颈癌HeLa229、ME-180、SiHa、 SW756细胞较宫颈上皮Ect1/E6E7细胞DNMT1表达水平及SOX1甲基化比例增高,SOX1蛋白表达降低（P＜0.05）。 与空白组、DNMT1-NC组比较,DNMT1-siRNA组HeLa229和SW756细胞体外克隆形成数、迁移和侵袭数量减少,裸 鼠内瘤体质量减轻,DNMT1、c-Myc、Cyclin D1、核/质β-catenin蛋白表达及SOX1甲基化比例降低,SOX1蛋白表达增 加（P＜0.05）。结论 DNMT1在CC组织和细胞中高表达,可能通过维持SOX1启动区高甲基化并抑制其蛋白表达, 促进CC生长和转移。     

异硫氰酸苯己酯诱导Molt-4细胞p15基因去甲基化及机制研究

研究新型组蛋白去乙酰化酶抑制剂异硫氰酸苯己酯（PHI）对急性T淋巴细胞性白血病Molt-4细胞p15基因的去甲基化作用及诱导沉默基因重新表达作用,并进一步探讨其作用机制。应用甲基化特异性聚合酶链反应（MSP）检测PHI作用前后Molt-4细胞株p15基因甲基化状态的变化;半定量逆转录-聚合酶链反应（RT-PCR）检测Molt-4细胞经过PHI处理后DNA甲基转移酶DNMT1、DNMT3A、DNMT3B、p15基因的mRNA的表达变化;用蛋白免疫印迹（Western blotting）检测Molt-4细胞经过PHI处理后的P15蛋白的表达。结果显示,PHI作用于Molt-4细胞5 d后,p15基因的甲基化程度减弱,p15基因的异常高甲基化现象被逆转,沉默的p15基因重新表达,p15 mRNA、P15蛋白表达增加,并呈浓度依赖性;PHI可下调DNMT1和DNMT3B的mRNA表达（P < 0.05）,而对DNMT3A的mRNA表达作用不明显（P > 0.05）。PHI可能通过抑制DNA甲基转移酶DNMT1和DNMT3B的活性,诱导p15基因产生去甲基化,或者（和）是通过改变p15基因附近组蛋白的乙酰化水平,导致染色体空间结构发生变化,增加转录因子的进入,从而诱导p15基因重新表达。
     

甲氨蝶呤治疗类风湿关节炎对Th17细胞甲基化的影响及其机制

目的： 探讨甲氨蝶呤片（MTX）治疗类风湿关节炎（RA）对Th17细胞DNA甲基化的影响及其机制。方法： 将2018年3月至2019年3月在某院住院治疗的67例使用MTX口服治疗的RA患者作为观察对象。采集患者治疗前后静脉血检测红细胞沉降率（ESR）、C反应蛋白（CRP）、血小板计数（PLT）及白细胞介素-17（IL-17），分离外周血单个核细胞（PBMC）测定Th17细胞比例，分析PBMC中维甲酸相关孤核受体-γt（ROR-γt）、DNA甲基转移酶1（DNMT1）、DNMT3a、DNMT3b基因mRNA表达水平，并检测ROR-γt基因甲基化程度，分别对患者Th17细胞比例与ESR、CRP、PLT及IL-17水平和ROR-γt基因甲基化程度与IL-17水平进行相关性分析。结果： 患者治疗前Th17细胞DNA甲基化程度低，ESR快，CRP及PLT水平高，Th17细胞比例及IL-17水平高，DNMT1基因mRNA表达水平低，ROR-γt基因mRNA表达水平高，ROR-γt基因甲基化比例低；治疗后ESR、CRP及PLT水平显著降低（P<0.05），Th17细胞比例及IL-17水平显著降低（P<0.001），DNMT1基因mRNA表达水平显著升高（P<0.001），ROR-γt基因mRNA表达水平显著降低（P<0.001），ROR-γt基因甲基化比例显著增加（P<0.05）；Th17细胞比例与IL-17水平呈正相关，ROR-γt基因甲基化程度与IL-17水平呈负相关（P<0.05）。结论： 甲氨蝶呤可通过提高类风湿关节炎患者Th17细胞ROR-γt基因甲基化程度抑制体内IL-17分泌改善和延缓疾病进程，同时此过程有DNMT1酶参与。     

转录因子EB在衰老心肌细胞自噬中的作用机制研究

目的 探讨转录因子EB(TFEB)在衰老心肌细胞自噬中的作用机制。方法 动物实验：将20只老年Wistar大鼠采取随机数字表法分为假手术组（Sham组）和缺血再灌注组（I/R组）。细胞实验：（1）体外培养大鼠心肌细胞，采用8 g/L D-半乳糖孵育8 d后分为常氧（Normoxia）组和缺氧/复氧（H/R）组。（2）在衰老心肌细胞中分别转染过表达和干扰TFEB腺病毒分为过表达对照（Ad-GFP）组、过表达对照+缺氧/复氧（Ad-GFP+H/R）组、过表达TFEB(AdTFEB)组、过表达TFEB+缺氧/复氧（Ad-TFEB+H/R）组、干扰对照（sh-NC）组、干扰对照+缺氧/复氧（sh-NC+H/R）组、干扰TFEB(sh-TFEB)组、干扰TFEB+缺氧/复氧（sh-TFEB+H/R）组。（3）分别用DNMT1、DNMT3a、DNMT3b的特异性抑制剂DC-05、TFD、NA处理缺氧/复氧后的衰老心肌细胞分为H/R组、DC-05组、TFD组、NA组。（4）在衰老心肌细胞中转染干扰DNMT3b腺病毒分为干扰对照（sh-NC）组、干扰对照缺氧/复氧（sh-NC+H/R）组、干扰DNMT...     

Phenylhexyl isothiocyanate induces gene p16 demethylation by down-regulating DNA methyltransferases in U266 cells

目的 研究异硫氰酸苯己酯(PHI)对骨髓瘤U266细胞株P16基因的去甲基化作用并探讨其作用机制.方法 应用半定量逆转录-聚合酶链反应检测U266 细胞经过PHI 处理后DNA 甲基转移酶DNMT1、DNMT3a 和DNMT3b基因的mRNA 的表达变化,用甲基化特异性聚合酶链反应检测PHI 作用前后U266细胞株P16 基因甲基化状态的变化.结果 使用不同浓度的PHI处理U266细胞72 h后,U266细胞表达DNMT1、DNMT3a、DNMT3b mRNA的水平明显降低并呈浓度依赖性.以不同浓度的PHI处理U266细胞10d后,P16基因的甲基化状态被逐渐逆转.结论 PHI 可能通过抑制DNA 甲基转移酶的表达水平诱导P16 基因产生去甲基化,使失活的抑癌基因重新激活,诱导瘤细胞凋亡.     

表没食子儿茶素没食子酸酯对脂肪肝细胞甲基化转移酶的调控作用

目的 探讨表没食子儿茶素没食子酸酯(EGCG)降低脂肪肝细胞脂肪含量的DNA甲基化调控机制,为应用EG CG防治脂肪肝提供实验依据.方法 利用游离脂肪酸棕榈酸处理大鼠正常肝细胞株BRL,建立大鼠脂肪肝细胞模型.用EGCG干预细胞72 h,检测处理前后脂肪肝细胞的脂肪含量及葡萄糖消耗量,用实时PCR方法检测EGCG作用前后DNA甲基化转移酶DNMT1、DNMT3a和DNMT3b的转录水平.结果 浓度为0.1 mmol/L的棕榈酸处理大鼠肝细胞BRL后,细胞的脂肪含量明显增加,吸光度(A)值从(0.22±0.04)增加到(0.31±0.06),差异具有统计学意义(P＜0.05),葡萄糖消耗量从(2.09±0.09)下降到(0.77±0.04),差异具有统计学意义(P＜0.01),即成功建立了脂肪肝细胞模型.EGCG干预脂肪肝细胞后,细胞的脂质含量明显减少,A值下降到(0.24±0.07) mM(P＜0.05),葡萄糖消耗量增加到(1.67 ±0.07)mM(P＜0.05),与DNA甲基化转移酶抑制剂5-Aza-2'-deoxycytidine(5-Aza-CdR)具有相同的效应.DNA甲基化转移酶DNMT1和DNMT3a基因在大鼠脂肪肝细胞中的mRNA表达水平分别增加了1.5和6倍(P＜0.05),EGCG和5-Aza-CdR均能够明显降低这两个基因的表达.DNMT3b在各处理组中没有明显差异.结论 EGCG可能通过抑制DNA甲基转移酶DNMT1和DNMT3a的表达,对脂肪和葡萄糖代谢中的关键基因去甲基化并使这些基因的表达上调,从而改善细胞内脂质沉积和胰岛素抵抗的状态.     

Aberrant methylation accounts for cell adhesion-related gene silencing during 3-methylcholanthrene and diethylnitrosamine induced multistep rat lung carcinogenesis associated with overexpression of DNA methyltransferases 1 and 3a

To evaluate the significance of alterations in cell adhesion-related genes methylation during lung multistep carcinogenesis induced by the genotoxic carcinogens 3-methylcholanthrene (MCA) and diethylnitrosamine (DEN), tissue samples microdissected from MCA/DEN-induced rat lung carcinogenesis model were subjected to methylation-specific PCR to evaluate the DNA methylation status of CADM1, TIMP3, E-cadherin and N-cadherin. Immunohistochemistry was used to determine protein expression of CADM1, TIMP3, N-cadherin and the DNA methyltransferases (DNMTs) 1, 3a and 3b. E-cadherin hypermethylation was not detected in any tissue. CADM1, TIMP3 and N-cadherin hypermethylation was correlated with the loss of their protein expression during the progression of pathologic lesions. The prevalence of DNA methylation of at least one gene and the average number of methylated genes increased with the histological progression. DNMT1 and DNMT3a protein expression increased progressively during the stages of lung carcinogenesis, whereas DNMT3b overexpression was only found in several samples. Furthermore, DNMT1 protein expression levels were correlated with CADM1 methylation, and DNMT3a protein expression levels were correlated with CADM1, TIMP3 and N-cadherin methylation. The average number of methylated genes during carcinogenesis was significantly correlated with DNMT1 and DNMT3a protein expression levels. Moreover, mRNA expression of CADM1 significantly increased after treatment with DNMT inhibitor 5-aza-2′-deoxycytidine in CADM1-methylated primary tumor cell lines. Our findings suggest that an accumulation of hypermethylation accounts for cell adhesion-related gene silencing is associated with dynamic changes in the progression of MCA/DEN-induced rat lung carcinogenesis. We suggest that DNMT1 and DNMT3a protein overexpression may be responsible for this aberrant DNA methylation.     

Effects of subchronic cadmium poisoning on DNA methylation in hens

Cadmium is a persistent pollutant that poses a threat to most biological organisms including birds. Although toxicity of cadmium is mainly linked to cancer, the mechanism of its carcinogenic activity remains poorly understood. Since DNA methylation is linked to cancer, we have examined the effect of cadmium on DNA methylation and DNMTs mRNA expression in hen liver and kidney. Sixty 50-day-old hyline-white hens were randomly allocated into 3 equal groups; a control group fed a basal diet, a low-dose group fed the basal diet spiked with 140 mg/kg CdCl₂, and a high-dose group fed the basal diet spiked with 210 mg/kg CdCl₂. After 60 days, liver and kidney samples were analysed for cadmium by FAAS, DNA methylation level by HPLC and DNMTs mRNA levels by semi-quantitative RT-PCR. The DNA methylation levels and the expressions of DNMT1 and DNMT3a mRNA in liver and kidney were significantly elevated by the cadmium treatment but there was no change in the expression of DNMT3b mRNA in the two tissues. The fact that cadmium increases DNA methylation and the expressions of DNMT1 and DNMT3a mRNA in liver and kidney suggests DNA methylation may be involved in the carcinogenic action of cadmium.     

5-氮杂-2′-脱氧胞苷对人甲状腺癌裸鼠移植瘤的抑制作用及其机制的研究#br#

目的　观察去甲基化制剂5-氮杂-2′-脱氧胞苷（5-Aza-CdR）对人甲状腺乳头状癌TPC-1细胞裸鼠移植瘤的生长抑制作用。方法　将人甲状腺乳头状癌TPC-1细胞接种于16只BALB/c雌性裸鼠右前肢腋下。移植瘤模型建立后,用随机数字表法将裸鼠分为2组,实验组按照1 μg/g腹腔注射5-Aza-CdR 200 μL,每2 d给药1次,给药4周。对照组腹腔注射等体积生理盐水。末次给药后处死荷瘤鼠,观察2组裸鼠移植瘤的生长情况,HE染色观察移植瘤的病理形态学改变,采用甲基化特异性PCR检测死亡相关蛋白激酶（DAPK）基因甲基化程度,采用免疫组化染色与Western blot检测DAPK和DNA甲基转移酶（DNMTs）的蛋白表达水平。结果　经药物干预4周后,实验组移植瘤体积和质量均较对照组明显减少（P＜0.05）,相比对照组,实验组抑瘤率为45.38%。HE染色结果显示,实验组肿瘤细胞数量减少,部分区域肿瘤细胞核淡染、缩小,局部出现核固缩、核溶解。实验组DAPK基因甲基化程度低于对照组。免疫组化染色和Western blot结果显示,实验组DAPK蛋白表达量明显高于对照组,DNMT1、DNMT3A蛋白表达量低于对照组,差异有统计学意义（均P＜0.05）,2组DNMT3B的表达差异无统计学意义（P＞0.05）。结论　5-Aza-CdR可通过调节裸鼠移植瘤内DNMTs来提高DAPK的表达,从而抑制甲状腺乳头状癌生长。     

Ultraviolet B decreases DNA methylation level of CD4+ T cells in patients with systemic lupus erythematosus

Objective

In the present study, DNA methylation level of CD4+ T cells exposed to ultraviolet B (UVB) was investigated and its potential mechanisms were also explored.

Methods

CD4+ T cells from 12 cases of healthy subjects and 33 cases of SLE patients were isolated and exposed to different dosages (0, 50, 100 mJ/cm²) of UVB. Further, SLE patients were divided into two groups: active SLE group (22 cases, SLEDAI scores >4) and inactive SLE group (11 cases, SLEDAI scores ≤4). DNA methylation was evaluated by the Methylamp? Global DNA Methylation Quantification Ultra Kit. The mRNA and protein expression levels of DNA methyltransferases (DNMT1 and DNMT3A) were detected by real-time PCR and western blot, respectively.

Results

The levels of DNA methylation and DNMT3A mRNA in SLE patients were significantly decreased compared with those in healthy subjects at baseline. After different dosages of ultraviolet irradiation (0, 50 and 100 mJ/cm²), DNA methylation levels of CD4+ T cells were all reduced in a dose-dependent manner in three subgroups. Additionally, 100 mJ/cm² ultraviolet irradiation in active SLE group contributed to a significant decrease of both DNA methylation and DNMT3A mRNA levels in CD4+ T cells. UVB exposure had no significant effects on expression levels of DNMT1 mRNA and protein and DNMT3A protein.

Conclusion

UVB decreases DNA methylation level of CD4+ T cells in SLE patients probably via inhibiting DNMT3A mRNA expression level, which needs to be further explored.

     

Analysis of aberrant methylation in DNA repair genes during malignant transformation of human bronchial epithelial cells induced by cadmium

Cadmium (Cd) and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood yet. Aberrant methylation was investigated in order to obtain insight into the DNA repair-related epigenetic mechanisms underlying CdCl(2)-induced malignant transformation of human bronchial epithelial cells (16HBE). Gene expression and DNA methylation were assessed in untreated control cells; 5th, 15th, and 35th passage of CdCl2-treated cells and tumorigenic cells (TCs) from nude mice by using high-performance liquid chromatography, real-time PCR, Western blot analysis, and methylation-specific PCR assay. During Cd-induced malignant transformation, global DNA methylation progressively increased and was associated with the overexpression of the DNA methyltransferase genes DNMT1 and DNMT3a but not DNMT3b. Expression of both the messenger RNA and proteins of the DNA repair genes (hMSH2, ERCC1, XRCC1, and hOGG1) progressively reduced and DNA damage increased with Cd-induced transformation. The promoter regions of hMSH2, ERCC1, XRCC1, and hOGG1 were heavily methylated in the 35th passage transformed cells and the TCs. The DNA demethylating agent 5-aza-2'-deoxycytidine could reverse the Cd-induced global DNA hypermethylation, DNMT hyperactivity, and the silencing of hMSH2, ERCC1, XRCC1, and hOGG1 in a time-dependent manner. The results indicate that DNMT1 and DNMT3a overexpression can result in global DNA hypermethylation and silencing of the hMSH2, ERCC1, XRCC1, and hOGG1 genes. They may partly explain the epigenetic mechanisms underlying the carcinogenesis due to Cd.     

激动黑皮质素4型受体对抗脓毒症诱导的肾脏损伤

目的:观察激动黑皮质素4型受体(MC4R)对抗脓毒症诱导的肾脏损伤作用,并探讨其机制.方法:雄性SD大鼠24只,随机分为:假手术组(Sham)、Sham+MC4R激动剂R027-3225组、盲肠结扎穿孔组(CLP)和CLP+R027-3225组,造模24 h后测定血清尿素氮(BUN)和肌酐(CRE)水平,HE染色观察肾脏形态学变化,免疫组化观察肾小管细胞NF-κB P65的表达,RT-PCR测定肾脏组织NF-κB mRNA表达情况.结果:与Sham组相比,CLP组血清BUN和CRE水平明显升高(P＜0.01),组织切片显示CLP组大鼠肾小体中血管球淤血、皱缩、肾小囊腔扩大,伴肾小管上皮细胞肿胀和坏死.肾脏组织NF-κB P65表达呈强阳性,NF-κB mRNA表达增高(P＜0.01).与CLP组相比,CLP+R027-3225组BUN和CRE水平下降(P＜0.01),肾小体、肾小管损伤减轻,肾脏组织NF-κB P65表达和NF-κB mRNA表达下降(P＜0.01).结论:脓毒症大鼠肾脏功能受损,激动MC4R可对抗脓毒症诱导的肾脏损伤,这可能与减少NF-κB的表达,降低炎症反应有关.