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Articles by D Zhang
Total Records ( 10 ) for D Zhang
  J Wei , M Xu , D Zhang and H. Mi

Carotenoid isomerase (CRTISO) has been suggested to protect photosystem II (PS II) from photodamage, probably through its product lutein. However, the mechanism of the photoprotection still remains to be further elucidated. In this work, we cloned a point mutated gene reported to encode a CRTISO which is responsible for the accumulation of lutein in rice mutant zel1 by a map-based cloning approach. The mutant phenotype was rescued by transformation with the corresponding gene of the wild type (WT). The activity of photosynthetic oxygen evolution was evidently suppressed in zel1. The amount of the core protein of PS II CP47 was much lower in all the PS II complexes especially in the LHCII-PS II supercomplexes and CP43-free PS II of zel1 than that of WT. On the other hand, the amount of another core protein of PS II CP43 of zel1 was decreased in the higher supercomplexes, whereas it was increased in the lower ones and PS II monomer. The immunodetection displayed that CP43, CP47, and the oxygen-evolving extrinsic proteins PsbO and PsbP were reduced, but the amount of reaction center protein D1 did not show significant change in zel1. Northern blot analysis showed that the transcriptional level of CP43 was down-regulated but not that of CP47 or D1 in zel1. In addition, the plastoquinone (PQ) QA was in a reduced state in zel1. On the basis of the results, we suggest that CRTISO might function in regulating the transcription of CP43 and the translation of CP47 by affecting the redox state of the PQ to stabilize the extrinsic proteins of oxygen evolution complexes in the rice plant.

  F. R Jornayvaz , M. J Jurczak , H. Y Lee , A. L Birkenfeld , D. W Frederick , D Zhang , X. M Zhang , V. T Samuel and G. I. Shulman

Low-carbohydrate, high-fat ketogenic diets (KD) have been suggested to be more effective in promoting weight loss than conventional caloric restriction, whereas their effect on hepatic glucose and lipid metabolism and the mechanisms by which they may promote weight loss remain controversial. The aim of this study was to explore the role of KD on liver and muscle insulin sensitivity, hepatic lipid metabolism, energy expenditure, and food intake. Using hyperinsulinemic-euglycemic clamps, we studied insulin action in mice fed a KD or regular chow (RC). Body composition was assessed by 1H magnetic resonance spectroscopy. Despite being 15% lighter (P < 0.001) than RC-fed mice because of a 17% increase in energy expenditure (P < 0.001), KD-fed mice manifested severe hepatic insulin resistance, as reflected by decreased suppression (0% vs. 100% in RC-fed mice, P < 0.01) of endogenous glucose production during the clamp. Hepatic insulin resistance could be attributed to a 350% increase in hepatic diacylglycerol content (P < 0.001), resulting in increased activation of PKC (P < 0.05) and decreased insulin receptor substrate-2 tyrosine phosphorylation (P < 0.01). Food intake was 56% (P < 0.001) lower in KD-fed mice, despite similar caloric intake, and could partly be attributed to a more than threefold increase (P < 0.05) in plasma N-acylphosphatidylethanolamine concentrations. In conclusion, despite preventing weight gain in mice, KD induces hepatic insulin resistance secondary to increased hepatic diacylglycerol content. Given the key role of nonalcoholic fatty liver disease in the development of type 2 diabetes and the widespread use of KD for the treatment of obesity, these results may have potentially important clinical implications.

  D Zhang , X Jiang , P Fang , Y Yan , J Song , S Gupta , A. I Schafer , W Durante , W. D Kruger , X Yang and H. Wang

Background— Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular disease. Monocytes display inflammatory and resident subsets and commit to specific functions in atherogenesis. In this study, we examined the hypothesis that HHcy modulates monocyte heterogeneity and leads to atherosclerosis.

Methods and Results— We established a novel atherosclerosis-susceptible mouse model with both severe HHcy and hypercholesterolemia in which the mouse cystathionine β-synthase (CBS) and apolipoprotein E (apoE) genes are deficient and an inducible human CBS transgene is introduced to circumvent the neonatal lethality of the CBS deficiency (Tg-hCBS apoE–/– Cbs–/– mice). Severe HHcy accelerated atherosclerosis and inflammatory monocyte/macrophage accumulation in lesions and increased plasma tumor necrosis factor- and monocyte chemoattractant protein-1 levels in Tg-hCBS apoE–/– Cbs–/– mice fed a high-fat diet. Furthermore, we characterized monocyte heterogeneity in Tg-hCBS apoE–/– Cbs–/– mice and another severe HHcy mouse model (Tg-S466L Cbs–/–) with a disease-relevant mutation (Tg-S466L) that lacks hyperlipidemia. HHcy increased monocyte population and selective expansion of inflammatory Ly-6Chi and Ly-6Cmid monocyte subsets in blood, spleen, and bone marrow of Tg-S466L Cbs–/– and Tg-hCBS apoE–/– Cbs–/– mice. These changes were exacerbated in Tg-S466L Cbs–/– mice with aging. Addition of l-homocysteine (100 to 500 µmol/L), but not l-cysteine, maintained the Ly-6Chi subset and induced the Ly-6Cmid subset in cultured mouse primary splenocytes. Homocysteine-induced differentiation of the Ly-6Cmid subset was prevented by catalase plus superoxide dismutase and the NAD(P)H oxidase inhibitor apocynin.

Conclusion— HHcy promotes differentiation of inflammatory monocyte subsets and their accumulation in atherosclerotic lesions via NAD(P)H oxidase–mediated oxidant stress.

  J Le , D Zhang , S Menees , J Chen and G. Raghuveer

Background— Obesity and familial dyslipidemia in children are associated with accelerated atherosclerosis by pathological examination. We sought to determine whether these children had increased carotid artery intima-media thickness (CIMT), a measure of subclinical atherosclerosis similar to 45-year-old adults. Adult CIMT percentile tables were used for comparison because normative CIMT data for children are limited.

Methods and Results— Seventy children, ages 6 to 19 years, with obesity- and atherosclerosis-promoting risk factors such as dyslipidemia, hypertension, insulin resistance, and tobacco smoke exposure, or with familial dyslipidemia, underwent carotid artery ultrasound. Advanced "vascular age" (VA) was defined as having maximum CIMT that was ≥25th percentile for race- and sex-matched 45-year-old adults. Mean age was 13.0±3.3 years. Forty (57%) of 70 children had body mass index ≥95th percentile for age and sex. Maximum CIMT for obese children was 0.53±0.05 mm and for familial dyslipidemic children was 0.52±0.04 mm. Advanced VA was seen in 30 (75%) of obese children and 22 (73%) of familial dyslipidemic children. Thirty (75%) of obese children had >3 mutable atherosclerosis-promoting risk factors; these children had a nonsignificantly higher maximum CIMT compared with obese children with ≤3 risk factors (0.54±0.06 mm versus 0.52±0.03 mm, P=0.07). Obese children with high fasting triglyceride levels were more likely to have advanced VA.

Conclusions— VA is advanced and comparable in obese children with atherosclerosis-promoting risk factors and in children with familial dyslipidemia. Advanced VA is prevalent in obese children with high fasting triglyceride levels.

  H Wang , D Zhang , W Wu , J Zhang , D Guo , Q Wang , T Jing , C Xu , X Bian and K. Yang

Steroid receptor coactivator-3 (SRC-3) has been reported to be overexpressed in the development and progression of many tumor types. SRC-3 has been detected in several lung cancer cell lines, but its expression and clinical significance in non–small cell lung cancer (NSCLC) remain unclear. In this study, 48 NSCLC tissues were collected and tissue microarrays were performed. The expression of SRC-3 was examined using nickel-intensified IHC. The results showed that of these 48 cases, 18 (37.5%) exhibited high levels of SRC-3 immunoreactivity, 23 (47.9%) exhibited moderate levels of SRC-3 immunoreactivity, and 7 (14.6%) were negative; thus, the total frequency of SRC-3 overexpression was 85.4% (41/48). This SRC-3 overexpression frequency was similar to the overexpression frequency observed for squamous cell carcinoma and adenocarcinoma (82.1% vs 90%) and for metastasis and non-metastasis patients (84.6% vs 85.7%). Data analysis demonstrated a significantly higher overexpression frequency in male patients compared with that in female patients (88.6% vs 76.9%). However, female patients tended to have higher expression levels of SRC-3, as measured by immunoreactivity, than male patients. These results demonstrate a high frequency of SRC-3 overexpression in NSCLC with a gender difference, suggesting that there is a specific role for SRC-3 in the pathogenesis of NSCLC. (J Histochem Cytochem 58:1121–1127, 2010)

  M. D Fox , D Zhang , A. Z Snyder and M. E. Raichle

Resting state studies of spontaneous fluctuations in the functional MRI (fMRI) blood oxygen level dependent (BOLD) signal have shown great promise in mapping the brain's intrinsic, large-scale functional architecture. An important data preprocessing step used to enhance the quality of these observations has been removal of spontaneous BOLD fluctuations common to the whole brain (the so-called global signal). One reproducible consequence of global signal removal has been the finding that spontaneous BOLD fluctuations in the default mode network and an extended dorsal attention system are consistently anticorrelated, a relationship that these two systems exhibit during task performance. The dependence of these resting-state anticorrelations on global signal removal has raised important questions regarding the nature of the global signal, the validity of global signal removal, and the appropriate interpretation of observed anticorrelated brain networks. In this study, we investigate several properties of the global signal and find that it is, indeed, global, not residing preferentially in systems exhibiting anticorrelations. We detail the influence of global signal removal on resting state correlation maps both mathematically and empirically, showing an enhancement in detection of system-specific correlations and improvement in the correspondence between resting-state correlations and anatomy. Finally, we show that several characteristics of anticorrelated networks including their spatial distribution, cross-subject consistency, presence with modified whole brain masks, and existence before global regression are not attributable to global signal removal and therefore suggest a biological basis.

  S Li , D Zhang , L Yang , J. V Burnier , N Wang , R Lin , E. R Lee , R. I Glazer and P. Brodt

The IGF-I receptor (IGF-IR) was identified as a tumor progression factor, but its role in invasion and metastasis has been the subject of some controversy. Previously we reported that in murine lung carcinoma M-27 cells, overexpression of IGF-IR increased the synthesis and activation of matrix metalloproteinase (MMP)-2 via Akt/phosphatidylinositol 3-kinase signaling. In contrast, we show here that in these and other cells, IGF-IR overexpression reduced the constitutive and phorbol 12-myristate 13-acetate (PMA)-inducible expression of three protein kinase C (PKC)-regulated metalloproteinases, MMP-3, MMP-9, and MMP-13, in cultured cells as well as in vivo in sc tumors. To elucidate the underlying mechanism, we analyzed the effect of IGF-IR on PKC expression and activity using wild-type and IGF-IR-overexpressing (M-27IGFIR) tumor cells. Our results show that overexpression and activation of IGF-IR reduced PKC- expression, PKC activity, and downstream ERK1/2 signaling, and these effects were reversed in cells expressing kinase (Y1131,1135,1136F) or C-terminal (Y1250/51F) domain mutants of IGF-IR. This reduction was due to transcriptional down-regulation of PKC- as evidenced by reduced PKC- mRNA expression in a phosphatidylinositol 3-kinase-dependent manner and a blockade of PKC- promoter activation as revealed by a reporter gene assay. Finally, reconstitution of PKC- levels could restore MMP-9 expression levels in these cells. Collectively, these results show that IGF-IR can inhibit PKC- gene transcription and thereby block the synthesis of PMA-regulated MMPs, suggesting that within the same cells, IGF-IR can act as both a positive and negative regulator of MMP expression and function.

  D Zhang , J. T Popesku , C. J Martyniuk , H Xiong , P Duarte Guterman , L Yao , X Xia and V. L. Trudeau

Teleost fish represent unique models to study the role of neuroestrogens because of the extremely high activity of brain aromatase (AroB; the product of cyp19a1b). Aromatase respectively converts androstenedione and testosterone to estrone and 17β-estradiol (E2). Specific inhibition of aromatase activity by fadrozole has been shown to impair estrogen production and influence neuroendocrine and reproductive functions in fish, amphibians, and rodents. However, very few studies have identified the global transcriptomic response to fadrozole-induced decline of estrogens in a physiological context. In our study, sexually mature prespawning female goldfish were exposed to fadrozole (50 µg/l) in March and April when goldfish have the highest AroB activity and maximal gonadal size. Fadrozole treatment significantly decreased serum E2 levels (4.7 times lower; P = 0.027) and depressed AroB mRNA expression threefold in both the telencephalon (P = 0.021) and the hypothalamus (P = 0.006). Microarray expression profiling of the telencephalon identified 98 differentially expressed genes after fadrozole treatment (q value <0.05). Some of these genes have shown previously to be estrogen responsive in either fish or other species, including rat, mouse, and human. Gene ontology analysis together with functional annotations revealed several regulatory themes for physiological estrogen action in fish brain that include the regulation of calcium signaling pathway and autoregulation of estrogen receptor action. Real-time PCR verified microarray data for decreased (activin-βA) or increased (calmodulin, ornithine decarboxylase 1) mRNA expression. These data have implications for our understanding of estrogen actions in the adult vertebrate brain.

  W Lu , P Ran , D Zhang , G Peng , B Li , N Zhong and J. Wang

In pulmonary arterial smooth muscle cells (PASMCs), Ca2+ influx through store-operated Ca2+ channels thought to be composed of canonical transient receptor potential (TRPC) proteins is an important determinant of intracellular free calcium concentration ([Ca2+]i) and pulmonary vascular tone. Sildenafil, a type V phosphodiesterase inhibitor that increases cellular cGMP, is recently identified as a promising agent for treatment of pulmonary hypertension. We previously demonstrated that chronic hypoxia elevated basal [Ca2+]i in PASMCs due in large part to enhanced store-operated Ca2+ entry (SOCE); moreover, ex vivo exposure to prolonged hypoxia (4% O2 for 60 h) upregulated TRPC1 and TRPC6 expression in PASMCs. We examined the effect of sildenafil on basal [Ca2+]i, SOCE, and the expression of TRPC in PASMCs under prolonged hypoxia exposure. We also examined the effect of sildenafil on TRPC1 and TRPC6 expression in pulmonary arterial smooth muscle (PA) from rats that developed chronically hypoxic pulmonary hypertension (CHPH). Compared with vehicle control, treatment with sildenafil (300 nM) inhibited prolonged hypoxia induced increases of 1) basal [Ca2+]i, 2) SOCE, and 3) mRNA and protein expression of TRPC in PASMCs. Moreover, sildenafil (50 mg · kg–1 · day–1) inhibited mRNA and protein expression of TRPC1 and TRPC6 in PA from chronically hypoxic (10% O2 for 21 days) rats, which was associated with decreased right ventricular pressure and right ventricular hypertrophy. Furthermore, we found, in PASMCs exposed to prolonged hypoxia, that knockdown of TRPC1 or TRPC6 by their specific small interference RNA attenuated the hypoxic increases of SOCE and basal [Ca2+]i, suggesting a cause and effect link between increases of TRPC1 and TRPC6 expression and the hypoxic increases of SOCE and basal [Ca2+]i. These results suggest that sildenafil may alter basal [Ca2+]i in PASMCs by decreasing SOCE through downregulation of TRPC1 and TRPC6 expression, thereby contributing to decreased vascular tone of pulmonary arteries during the development of CHPH.

  W Lu , P Ran , D Zhang , N Lai , N Zhong and J. Wang

Recent advances have identified an important role of bone morphogenetic protein 4 (BMP4) in pulmonary vascular remodeling, yet the underlying mechanisms remain largely unexplored. We have previously found that Ca2+ influx through store-operated calcium channels (SOCC), which are mainly thought to be composed of canonical transient receptor potential (TRPC) proteins, likely contribute to the pathogenic development of chronic hypoxic pulmonary hypertension. In this study, we investigated the effect of BMP4 on expression of TRPC and store-operated Ca2+ entry (SOCE) in pulmonary arterial smooth muscle cells (PASMCs). Real-time quantitative PCR and Western blotting revealed that treatment with BMP4 (50 ng/ml, 60 h) increased TRPC1, TRPC4, and TRPC6 mRNA and protein expression in growth-arrested rat distal PASMCs. Moreover, in comparison to vehicle control, cells treated with BMP4 also exhibited enhanced SOCE, and elevated basal intracellular calcium concentration ([Ca2+]i) as determined by fluorescent microscopy using the Ca2+ indicator Fura-2 AM. Perfusing cells with Ca2+-free Krebs-Ringer bicarbonate solution (KRBS) or KRBS containing SOCC antagonists SKF-96365 or NiCl2 attenuated the increases in basal [Ca2+]i caused by BMP4. Specific knockdown of BMP4 by small interference RNA significantly decreased the mRNA and protein expression of TRPC1, TRPC4, and TRPC6 and reduced SOCE and basal [Ca2+]i in serum-stimulated PASMCs. We conclude that BMP4 regulates calcium signaling in PASMCs likely via upregulation of TRPC expression, leading to enhanced SOCE and basal [Ca2+]i in PASMCs, and by this mechanism contributes to pulmonary vascular remodeling during pulmonary arterial hypertension.

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