Evidence that the human cutaneous venoarteriolar response is not mediated by adrenergic mechanisms

The venoarteriolar response causes vasoconstriction to skin and muscle via local mechanisms secondary to venous congestion. The purpose of this project was to investigate whether this response occurs through α-adrenergic mechanisms. In supine individuals, forearm skin blood flow was monitored via laser-Doppler flowmetry over sites following local administration of terazosin (α₁-antagonist), yohimbine (α₂-antagonist), phentolamine (non-selective α-antagonist) and bretylium tosylate (inhibits neurotransmission of adrenergic nerves) via intradermal microdialysis or intradermal injection. In addition, skin blood flow was monitored over an area of forearm skin that was locally anaesthetized via application of EMLA (2.5 % lidocaine (lignocaine) and 2.5 % prilocaine) cream. Skin blood flow was also monitored over adjacent sites that received the vehicle for the specified drug. Each trial was performed on a minimum of seven subjects and on separate days. The venoarteriolar response was engaged by lowering the subject's arm from heart level such that the sites of skin blood flow measurement were 34 ± 1 cm below the heart. The arm remained in this position for 2 min. Selective and non-selective α-adrenoceptor antagonism and presynaptic inhibition of adrenergic neurotransmission did not abolish the venoarteriolar response. However, local anaesthesia blocked the venoarteriolar response without altering α-adrenergic mediated vasoconstriction. These data suggest that the venoarteriolar response does not occur through adrenergic mechanisms as previously reported. Rather, the venoarteriolar response may due to myogenic mechanisms associated with changes in vascular pressure or is mediated by a non-adrenergic, but neurally mediated, local mechanism.     

携带人FL、GM-CSF基因的裸DNA的抑瘤作用

目的探讨可表达人FL和GM-CSF的裸DNA抑制小鼠移植肿瘤生长的作用。方法分别将带有信号肽序列的人FL和GM-CSF基因插入pcDNA3.1/zeo载体,构建分泌表达人FL和GM-CSF的治疗用表达载体,经SephacrylS1000柱层析法纯化了重组表达质粒。用Western印迹和ELISA法检测目的基因在293细胞中的表达,并用TF1细胞验证293细胞表达的GM-CSF的生物学活性。重组表达质粒与脂质体孵育形成复合物,隔天肌肉注射小鼠共6次,每只小鼠接种T细胞淋巴瘤细胞EL-4 2×105后,观察不同基因组合条件下肿瘤的生长情况。结果人FL和GM-CSF在293细胞中表达量分别为50μg/L和30μg/L,单用FL或GM-CSF和两者联用对肿瘤生长均有一定抑制作用,在第17天抑制率为30%~40%。联合应用组较单用FL或GM-CSF组更为有效抑制肿瘤生长,但小鼠生存时间并无延长。结论人FL和GM-CSF在293细胞中均获表达,且对肿瘤的早期生长具有一定的抑制作用,两者联合应用效果更为明显,但对小鼠最终生存时间并无影响。     

Expression of the osteoarthritis-associated gene GDF5 is modulated epigenetically by DNA methylation

GDF5 is involved in synovial joint development, maintenance and repair, and the rs143383 C/T single nucleotide polymorphism (SNP) located in the 5'UTR of GDF5 is associated, at the genome-wide significance level, with osteoarthritis susceptibility, and with other musculoskeletal phenotypes including height, congenital hip dysplasia and Achilles tendinopathy. There is a significant reduction in the expression of the disease-associated T allele relative to the C allele in synovial joint tissues, an effect influenced by a second SNP (rs143384, C/T) also within the 5'UTR. The differential allelic expression (DAE) imbalance of the C and T alleles of rs143383 varies intra- and inter-individually, suggesting that DAE may be modulated epigenetically. The C alleles of both SNPs form CpG dinucleotides that are potentially amenable to regulation by methylation. Here, we have examined whether DNA methylation regulates GDF5 expression and the allelic imbalance caused by rs143383. We observed methylation of the GDF5 promoter and 5'UTR in cell lines and joint tissues, with demethylation correlating with increased GDF5 expression. The CpG sites created by the C alleles at rs143383 and rs143384 were variably methylated, and treatment of a heterozygous cell line with a demethylating agent further increased the allelic expression imbalance between the C and T alleles. This demonstrates that the genetic effect of the rs143383 SNP on GDF5 expression is modulated epigenetically by DNA methylation. The variability in DAE of rs143383 is therefore partly accounted for by differences in DNA methylation that could influence the penetrance of this allele in susceptibility to common musculoskeletal diseases.     

Regulation of amylase gene expression in diabetic mice is mediated by a cis-acting upstream element close to the pancreas-specific enhancer.

We localized the cis-acting sequences that mediate the regulation of a pancreatic amylase gene, Amy-2.2, in diabetic mice. We constructed three hybrid genes containing sequences from the 5'-flanking region of the amylase gene upstream of the heterologous elastase promoter linked to the CAT structural gene. These constructs were transferred to the germ line of transgenic mice by microinjection of fertilized eggs. The amylase sequences had two effects on expression of the elastase promoter: Basal expression was increased, and expression in diabetic animals was reduced to approximately 2% of basal levels. A 30-bp amylase fragment was sufficient to transfer both of these regulatory functions to the elastase promoter. Sequences within this 30-bp fragment are included in the binding site for the pancreatic nuclear protein PTF1. The close association of the PTF1-binding site and the regulatory functions is consistent with a mechanism based on interference with activation by PTF1 in diabetic pancreas. PTF1-binding activity is not reduced in diabetic pancreas. The data presented here demonstrate that the 5'-flanking region of the pancreatic amylase gene contains a novel insulin-dependent element (IDE) that mediates the loss of expression in diabetic animals.     

The HIV-1 major splice donor D1 is activated by splicing enhancer elements within the leader region and the p17-inhibitory sequence

Usage of the HIV-1 major 5′ splice site D1 is a prerequisite for generation of all spliced viral mRNAs encoding essential regulatory and structural proteins. We set out to determine whether flanking sequences ensure D1-activation. We found that an exonic splicing enhancer function is exerted by the region upstream of D1, which is crucially required for its activation. Additionally, we identified an intronic splicing regulatory element within the p17-instability element of the Gag-ORF enhancing D1-activation. Furthermore, our experimental data demonstrated that sequence motifs displaying high similarity to consensus binding sites for SR protein SC35 (SRSF2) overlapping with D1 fine-tune its activation. Our results reveal that D1-activation is safe-guarded by the interplay of upstream and downstream located splicing enhancer elements ensuring usage of D1 even if its strength is decreased upon mutation. The identification of sequence elements activating D1-usage sheds further light on the balanced expression of alternatively spliced HIV-1 mRNAs.     

活性维生素D3对大鼠肺纤维化中蛋白激酶D1介导的抗氧化通路的影响

目的:探讨肺纤维化发生发展中蛋白激酶D1(PKD1)介导的线粒体抗氧化通路的作用以及活性维生素D3在纤维化过程中对该通路的影响。方法:雄性SD大鼠随机分成对照组、模型组和治疗组。应用实时荧光定量PCR和免疫组织化学分别从mRNA和蛋白质水平检测大鼠肺组织中PKD1、核转录因子(NF-κB)和锰超氧化物歧化酶(MnSOD)的表达。结果:在第14天,治疗组和模型组中PKD1、NF-κB和MnSOD的表达量都显著低于对照组,而治疗组中3种因子的表达量又明显高于模型组;在第21天,3种因子在模型组和治疗组中的表达量明显高于对照组。在第28天,3种因子在模型组和治疗组中的表达量与对照组相比两两之间均没有差异。结论:PKD1-MnSOD线粒体抗氧化通路在博莱霉素引起的大鼠肺纤维化早期发挥重要作用,活性维生素D3能够上调这一抗氧化通路,具有一定的抗氧化作用,对大鼠肺纤维化的发生发展具有一定的抑制作用。     

RNA干扰Rbl-2基因调控DNA甲基化转移酶介导心脏干细胞凋亡

目的:视网膜母细胞瘤样蛋白2(Rbl-2)在调控DNA甲基化转移酶(DNMT)中发挥重要作用,而DNMT影响干细胞的分化。本文旨在探讨调控Rbl-2基因的表达对心脏干细胞凋亡的影响。方法:分离培养人心脏干细胞,转染Rbl-2 siRNA。采用real time RT-PCR检测Rbl-2和DNMT-3B mRNA表达水平,Westernblotting检测DNMT-3B蛋白表达和caspase-3活化片段,并以Annexin V-FITC/PI双染色-流式细胞术检测细胞凋亡率。结果:在人心脏干细胞中,转染siRNA后Rbl-2 mRNA表达水平与阴性对照组相比显著降低(P0.01),同时DNMT-3B mRNA和蛋白表达水平与阴性对照组相比均显著升高(P0.01),差异显著。与阴性对照组相比,转染Rbl-2 siRNA的人心脏干细胞caspase-3激活,表现为caspase-3活性片段与caspase-3前体的比值显著增高(P0.01),annexin V阳性细胞凋亡率上升(P0.05)。结论:Rbl-2基因在心脏干细胞的生存中具有正性调控作用,抑制其表达能促进心脏干细胞的凋亡,其调控机制与表观遗传学的修饰密切相关。