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Articles by D Liu
Total Records ( 13 ) for D Liu
  Y Min , W Xu , D Liu , S Shen , Y Lu , L Zhang and H. Wang

Dendritic cells (DCs) are important for the initiation of the adaptive immune response against Mycobacterium tuberculosis. Autophagy is an innate and adaptive defense mechanism and important for the control of M. tuberculosis. However, the role of autophagy in the adaptive immune response against M. tuberculosis remains to be determined. In the present study, we studied the effects of autophagy on the maturation of DCs infected with Bacillus Calmette–Guérin (BCG). The phenotype and function of the DCs were assessed by measuring the expression of CD86 and HLA-DR and the secretion of IL-10 and IL-6. Autophagy was evaluated by the change in LC3II, a molecular marker for autophagy. Following stimulation of autophagy, DCs that were matured in the presence of BCG showed enhanced expression of CD86 and HLA-DR and increased IL-6 production. The expression of LC3II was increased after the stimulation of autophagy. These results demonstrated that autophagy might result in the increased maturation of BCG-infected DCs, suggesting that autophagy could contribute to an enhanced adaptive immune response against M. tuberculosis.

  J Huang , J Gao , X Lv , G Li , D Hao , X Yao , L Zhou , D Liu and R. Wang

Glioma-specific transcription of tumor-killing genes has been exploited as a promising gene therapeutic modality in glioma patients. Musashi1 (Msi1) and GFAP gene promoters are both cancer-specific promoters. Optimized HIF-binding site (optHBS) sequence was newly found as efficient as EPO HREs used as enhancer in cancer gene therapy. We constructed 4optHBS-Msi1/GFAP promoters and tested their ability to mediate BAX expression to induce apoptosis in glioma cell lines. Our results demonstrated that 4optHBS-Msi1/GFAP promoters are apparently strong and glioma-selective promoters with potential application in targeted glioma gene therapy, and 4optHBS-Msi1/GFAP-BAX are valuable tools for glioma gene therapy.

  J Yin , A Zuberi , Z Gao , D Liu , Z Liu and J. Ye

The extract of plant Shilianhua (SLH; Sinocrassula indica Berge) is a component in a commercial product for control of blood glucose. However, it remains to be investigated whether the SLH extract enhances insulin sensitivity in a model of type 2 diabetes. To address this question, the SLH crude extract was fractionated into four parts on the basis of polarity, and bioactivities of each part were tested in cells. One of the fractions, F100, exhibited a strong activity in the stimulation of glucose consumption in vitro. Glucose consumption was induced significantly by F100 in 3T3-L1 adipocytes, L6 myotubes, and H4IIE hepatocytes in the absence of insulin. F100 also increased insulin-stimulated glucose consumption in L6 myotubes and H4IIE hepatocytes. It increased insulin-independent glucose uptake in 3T3-L1 adipocytes and insulin-dependent glucose uptake in L6 cells. The glucose transporter-1 (GLUT1) protein was induced in 3T3-L1 cells, and the GLUT4 protein was induced in L6 cells by F100. Mechanism study indicated that F100 induced GSK-3β phosphorylation, which was comparable with that induced by insulin. Additionally, the transcriptional activity of NF-B was inhibited by F100. In RAW 264.7 macrophages, mRNA expression of NF-B target genes (TNF and MCP-1) was suppressed by F100. In KK.Cg-Ay/+ mice, F100 decreased fasting insulin and blood glucose and improved insulin tolerance significantly. We conclude that the F100 may be a bioactive component in the SLH plant. It promotes glucose metabolism in vitro and in vivo. Inhibition of GSK-3β and NF-B may be the potential mechanism.

  A. S Tsao , D Liu , J Martin , X. m Tang , J. J Lee , A. K El Naggar , I Wistuba , K. S Culotta , L Mao , A Gillenwater , Y. M Sagesaka , W. K Hong and V. Papadimitrakopoulou

Epidemiologic and preclinical data support the oral cancer prevention potential of green tea extract (GTE). We randomly assigned patients with high-risk oral premalignant lesions (OPL) to receive GTE at 500, 750, or 1,000 mg/m2 or placebo thrice daily for 12 weeks, evaluating biomarkers in baseline and 12-week biopsies. The OPL clinical response rate was higher in all GTE arms (n = 28; 50%) versus placebo (n = 11; 18.2%; P = 0.09) but did not reach statistical significance. However, the two higher-dose GTE arms [58.8% (750 and 1,000 mg/m2), 36.4% (500 mg/m2), and 18.2% (placebo); P = 0.03] had higher responses, suggesting a dose-response effect. GTE treatment also improved histology (21.4% versus 9.1%; P = 0.65), although not statistically significant. GTE was well tolerated, although higher doses increased insomnia/nervousness but produced no grade 4 toxicity. Higher mean baseline stromal vascular endothelial growth factor (VEGF) correlated with a clinical (P = 0.04) but not histologic response. Baseline scores of other biomarkers (epithelial VEGF, p53, Ki-67, cyclin D1, and p16 promoter methylation) were not associated with a response or survival. Baseline p16 promoter methylation (n = 5) was associated with a shorter cancer-free survival. Stromal VEGF and cyclin D1 expression were downregulated in clinically responsive GTE patients and upregulated in nonresponsive patients at 12 weeks (versus at baseline). An extended (median, 27.5 months) follow-up showed a median time to oral cancer of 46.4 months. GTE may suppress OPLs, in part through reducing angiogenic stimulus (stromal VEGF). Higher doses of GTE may improve short-term (12-week) OPL outcome. The present results support longer-term clinical testing of GTE for oral cancer prevention.

  J Zhou , Y Zhu , M Cheng , D Dinesh , T Thorne , K. K Poh , D Liu , C Botros , Y. L Tang , N Reisdorph , R Kishore , D. W Losordo and G. Qin

Background— Recent studies have identified a polymorphism in the endothelin-converting enzyme (ECE)–1b promoter (–338C/A) that is strongly associated with hypertension in women. The polymorphism is located in a consensus binding sequence for the E2F family of transcription factors. E2F proteins are crucially involved in cell-cycle regulation, but their roles in cardiovascular function are poorly understood. Here, we investigated the potential role of E2F2 in blood pressure regulation.

Methods and Results— Tail-cuff measurements of systolic and diastolic blood pressures were significantly higher in E2F2-null (E2F2–/–) mice than in their wild-type littermates, and in ex vivo ring assays, aortas from the E2F2–/– mice exhibited significantly greater contractility in response to big endothelin-1. Big endothelin-1 is activated by ECE-1, and mRNA levels of ECE-1b, the repressive ECE-1 isoform, were significantly lower in E2F2–/– mice than in wild-type mice. In endothelial cells, chromatin immunoprecipitation assays confirmed that E2F2 binds the ECE-1b promoter, and promoter-reporter assays indicated that E2F2 activates ECE-1b transcription. Furthermore, loss or downregulation of E2F2 led to a decline in ECE-1b levels, to higher levels of the membranous ECE-1 isoforms (ie, ECE-1a, -1c, and -1d), and to deregulated ECE-1 activity. Finally, Sam68 coimmunoprecipitated with E2F2, occupied the ECE-1b promoter (chromatin immunoprecipitation), and repressed E2F2-mediated ECE-1b promoter activity (promoter-reporter assays).

Conclusion— Our results identify a cell-cycle–independent mechanism by which E2F2 regulates endothelial function, arterial contractility, and blood pressure.

  J Pi , Y Bai , K. W Daniel , D Liu , O Lyght , D Edelstein , M Brownlee , B. E Corkey and S. Collins

Uncoupling protein (UCP) 2 is a widely expressed mitochondrial protein whose precise function is still unclear but has been linked to mitochondria-derived reactive oxygen species production. Thus, the chronic absence of UCP2 has the potential to promote persistent reactive oxygen species accumulation and an oxidative stress response. Here, we show that Ucp2–/– mice on three highly congenic (N >10) strain backgrounds (C57BL/6J, A/J, 129/SvImJ), including two independently generated sources of Ucp2-null animals, all exhibit increased oxidative stress. Ucp2-null animals exhibit a decreased ratio of reduced glutathione to its oxidized form in blood and tissues that normally express UCP2, including pancreatic islets. Islets from Ucp2–/– mice exhibit elevated levels of numerous antioxidant enzymes, increased nitrotyrosine and F4/80 staining, but no change in insulin content. Contrary to results in Ucp2–/– mice of mixed 129/B6 strain background, glucose-stimulated insulin secretion in Ucp2–/– islets of each congenic strain was significantly decreased. These data show that the chronic absence of UCP2 causes oxidative stress, including in islets, and is accompanied by impaired glucose-stimulated insulin secretion.

  E Workman , L Saieva , T. L Carrel , T. O Crawford , D Liu , C Lutz , C. E Beattie , L Pellizzoni and A. H.M. Burghes

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease. Loss of the survival motor neuron (SMN1) gene, in the presence of the SMN2 gene causes SMA. SMN functions in snRNP assembly in all cell types, however, it is unclear how this function results in specifically motor neuron cell death. Lack of endogenous mouse SMN (Smn) in mice results in embryonic lethality. Introduction of two copies of human SMN2 results in a mouse with severe SMA, while one copy of SMN2 is insufficient to overcome embryonic lethality. We show that SMN(A111G), an allele capable of snRNP assembly, can rescue mice that lack Smn and contain either one or two copies of SMN2 (SMA mice). The correction of SMA in these animals was directly correlated with snRNP assembly activity in spinal cord, as was correction of snRNA levels. These data support snRNP assembly as being the critical function affected in SMA and suggests that the levels of snRNPs are critical to motor neurons. Furthermore, SMN(A111G) cannot rescue Smn–/– mice without SMN2 suggesting that both SMN(A111G) and SMN from SMN2 undergo intragenic complementation in vivo to function in heteromeric complexes that have greater function than either allele alone. The oligomer composed of limiting full-length SMN and SMN(A111G) has substantial snRNP assembly activity. Also, the SMN(A2G) and SMN(A111G) alleles in vivo did not complement each other leading to the possibility that these mutations could affect the same function.

  D Liu , H Benlhabib and C. R. Mendelson

Estrogen-related receptor (ERR) plays a critical role in basal and cAMP-induced expression of the human surfactant protein-A (SP-A) gene in lung type II cells through direct binding to an ERR response element (ERRE, 5'-TGACCTTA-3') within its 5'-flanking region. Furthermore, protein kinase A (PKA) up-regulates ERR activation of the hSP-A promoter. In the present study, using cultured human fetal lung type II cells, we observed that cAMP enhanced ERR phosphorylation and nuclear expression levels. cAMP/PKA stimulation of ERR activation of the SP-A promoter was blocked by the PKA inhibitor, H89, whereas the MAPK P38 inhibitor, SB203580, and the MAPK kinase inhibitor, PD98059, had negligible to modest effects. This suggests that cAMP acts selectively through PKA to increase ERR transcriptional activity. Of several coactivators tested, steroid receptor coactivator 2 (SRC-2) had the most pronounced effect to increase ERR transcriptional activity at the SP-A promoter; this was enhanced by cotransfection with PKA catalytic subunit (PKAcat). Interestingly, SRC-2, ERR, and PKAcat in type II cell nuclear extracts interacted at the ERRE; this was enhanced by cAMP and inhibited by H89. cAMP increased in vivo binding of PKAcat and SRC-2 to the ERRE genomic region in lung type II cells. In mutagenesis studies, three serines (S87, S114, and S277) were found to be critical for PKA and SRC-2 induction of ERR transcriptional activity. Collectively, these findings indicate that cAMP/PKA signaling enhances ERR phosphorylation and nuclear localization, recruitment to the SP-A promoter, and interaction with PKAcat and SRC-2, resulting in the up-regulation of SP-A gene transcription.

  R Gohara , D Liu , K Nakashima , Y Takasaki and S. Ando

Organic compounds are used as templates to regulate the morphology of inorganic nanostructures. In the present study, we used intermediate filaments (IFs), the major cytoskeleton component of most eukaryotic cells, as a template for hollow silica nanotube preparation. Sol–gel polymerization of tetraethoxysilane proceeded preferentially on the surface of IFs assembled from vimentin protein in vitro, resulting in silica-coated fibres. After removing IFs by calcination, electron microscopy revealed hollow silica nanotubes several micrometers long, with outer diameters of 35–55 nm and an average inner diameter of 10 nm (comparable to that of IFs). Furthermore, the silica nanotubes exhibited a gnarled surface structure with an 18–26 nm repeating pattern (comparable to the 21-nm beading pattern along IFs). Thus, the characteristic morphology of IFs were well replicated into hollow silica nanotubes, suggesting that IFs maybe useful as an organic template.

  Y Wei , Y Ge , F Zhou , H Chen , C Cui , D Liu , Z Yang , G Wu , J Gu and J. Jiang

ATF5, a member of ATF/CREB family of b-ZIP transcription factors, is highly expressed in a wide variety of neoplasms and regulates cell differentiation, cell survival and apoptosis. However, the mechanism of human ATF5 transcriptional regulation has not been clarified. Here, we identified the transcription start site of the ATF5 gene, cloned its 5'-flanking region and identified the region –105 to +3 relative to the transcription start site as that having promoter activity. This region contained potential binding sites for several transcription factors, including EBF1, Sp1 and E2F1. EBF1 transcription factor binds to the ATF5 promoter and regulates the ATF5 transcription in an EBF-binding site independent manner. Thus, our studies not only provided molecular basis of ATF5 transcriptional regulation, but also identified ATF5 as a target gene of EBF1 transcription factor.

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