Biomedical subjects

Jia Chen

Publications and source records attributed to Jia Chen.

At least 55 records · Page 3Linked to original sources

PubMed2005

NADK2, an Arabidopsis chloroplastic NAD kinase, plays a vital role in both chlorophyll synthesis and chloroplast protection.

As one of terminal electron acceptors in photosynthetic electron transport chain, NADP receives electron and H(+) to synthesize NADPH, an important reducing energy in chlorophyll synthesis and Calvin cycle. NAD kinase (NADK), the catalyzing enzyme for the de novo synthesis of NADP from substrates NAD and ATP, may play an important role in the synthesis of NADPH. NADK activity has been observed in different sub-cellular fractions of mitochondria, chloroplast, and cytoplasm. Recently, two distinct NADK isoforms (NADK1 and NADK2) have been identified in Arabidopsis. However, the physiological roles of NADKs remain unclear. In present study, we investigated the physiological role of Arabidiposis NADK2. Sub-cellular localization of the NADK2-GFP fusion protein indicated that the NADK2 protein was localized in the chloroplast. The NADK2 knock out mutant (nadk2) showed obvious growth inhibition and smaller rosette leaves with a pale yellow color. Parallel to the reduced chlorophyll content, the expression levels of two POR genes, encoding key enzymes in chlorophyll synthesis, were down regulated in the nadk2 plants. The nadk2 plants also displayed hypersensitivity to environmental stresses provoking oxidative stress, such as UVB, drought, heat shock and salinity. These results suggest that NADK2 may be a chloroplast NAD kinase and play a vital role in chlorophyll synthesis and chloroplast protection against oxidative damage.

Amino Acid Sequence↗

PubMed2005

Charge transfer induced polarity switching in carbon nanotube transistors.

We probed the charge transfer interaction between the amine-containing molecules hydrazine, polyaniline, and aminobutyl phosphonic acid and carbon nanotube field effect transistors (CNTFETs). We successfully converted p-type CNTFETs to n-type and drastically improved the device performance in both the ON- and OFF-transistor states, utilizing hydrazine as dopant. We effectively switched the transistor polarity between p- and n- type by accessing different oxidation states of polyaniline. We also demonstrated the flexibility of modulating the threshold voltage (Vth) of a CNTFET by engineering various charge-accepting and -donating groups in the same molecule.

Amines↗

PubMed2005

Haplotype-phenotype relationships of paraoxonase-1.

Paraoxonase 1 (PON1) is an enzyme with multiple activities, including detoxification of organophosphates. It is believed to be important in preventing neurotoxic damage and has also been implicated in atherosclerosis. The PON1 gene contains five common polymorphisms, three in the promoter (-909G > C, -162A > G, -108C > T) and two in the coding region (M55L, Q192R) with varying but incomplete linkage disequilibrium. Our previous study showed that functional polymorphisms in PON1 were strongly associated with enzymatic activity in both pregnant women [26-30 weeks of gestation] and neonates. However, there was substantial overlapping of enzyme activities between genotypes. In this study, we investigated whether haplotype (genotype + phase) information would strengthen the genotype-phenotype relationship for PON1. The study consisted of a multiethnic population of 402 mothers and 229 neonates. Haplotypes were imputed by two widely used programs, PHASE and tagSNPs, which yielded very similar results. There were seven haplotypes with a frequency of 5% or higher in at least one ethnic group of the study population. Haplotype composition varied substantially with respect to ethnicity. Haplotypes in Caucasians and African-Americans showed the largest difference, and Caribbean Hispanics seemed to be a mixture of Caucasian and African ancestry. Collectively, the genetic (genotype or haplotype) contribution to PON1 enzymatic activity (measured as phenylacetate hydrolysis) was greater in neonates compared with mothers. Specifically, 16.6% of PON1 variability was explained by genotypes in mothers compared with 30.9% in neonates. Haplotype information offered a slightly increased power in predicting PON1 activity; they explained 35.5% and 19.3% of PON1 variability in neonates and mothers, respectively.

Adult↗

PubMed2005

AtHsfA2 modulates expression of stress responsive genes and enhances tolerance to heat and oxidative stress in Arabidopsis.

There is increasing evidence for considerable interlinking between the responses to heat stress and oxidative stress, and recent researches suggest heat shock transcription factors (Hsfs) play an important role in linking heat shock with oxidative stress signals. In this paper, we present evidence that AtHsfA2 modulated expression of stress responsive genes and enhanced tolerance to heat and oxidative stress in Arabidopsis. Using Northern blot and quantitative RT-PCR analysis, we demonstrated that the expression of AtHsfA2 was induced by not only HS but also oxidative stress. By functional analysis of AtHsfA2 knockout mutants and AtHsfA2 overexpressing transgenic plants, we also demonstrated that the mutants displayed reduced the basal and acquired thermotolerance as well as oxidative stress tolerance but the overexpression lines displayed increased tolerance to these stress. The phenotypes correlated with the expression of some Hsps and APX1, ion leakage, H202 level and degree of oxidative injuries. These results showed that, by modulated expression of stress responsive genes, AtHsfA2 enhanced tolerance to heat and oxidative stress in Arabidopsis. So we suggest that AtHsfA2 plays an important role in linking heat shock with oxidative stress signals.

Arabidopsis↗

PubMed2005

[A randomized trial comparing oxaliplatin plus vinorelbine versus cisplatin plus vinorelbine for the treatment of patients with advanced non-small-cell lung cancer].

OBJECTIVE: To evaluate the difference of efficacy, side-effects and quality of life in advanced non-small-cell lung cancer (NSCLC) patients treated with oxaliplatin plus vinorelbine or cisplatin plus vinorelbine. METHODS: Eligible patients were randomly assigned to NL (oxaliplatin + vinorelbine) group and NP (cisplatin + vinorelbine) group in a 2:1 ratio. In the NL group, 70 evaluable cases were treated with oxaliplatin 130 mg/m(2) i.v. on day 2, and vinorelbine 25 mg/m(2) i.v. on days 1 and 8 in 21 days per cycle. In the NP group, 32 evaluable cases were treated with cisplatin 80 mg/m(2) i.v. divided to 2 - 3 days dosing, 21 days per cycle, and vinorelbine administered by the same way as in the NL group. The response rate, time to progression (TTP), one-year survival, side-effects and the quality of life were observed. RESULTS: The response rate was 35.7% vs. 43.8% (P = 0.4), median TTP was 4.7 months vs. 5.5 months (P = 0.6), one-year survival rate was 38.5% vs. 58.6% (P = 0.07) in the NL and NP groups, respectively. Grade I-II neuro-sensory toxicity occurred significantly more frequent in NL group than in NP group (68.4% vs. 36.4%, P = 0.0017). However, Grade I-II granulocytopenia was significantly less occurred in NL group than in NP group (49.4% vs. 70.6%, P = 0.037). There was no statistically difference between the two groups regarding quality of life. CONCLUSION: Due to good efficacy and tolerability, the NL regimen offered a new candidate for treating advanced NSCLC.

Adolescent↗

PubMed2004

Extracellular calmodulin-induced stomatal closure is mediated by heterotrimeric G protein and H2O2.

Extracellular calmodulin (ExtCaM) exerts multiple functions in animals and plants, but the mode of ExtCaM action is not well understood. In this paper, we provide evidence that ExtCaM stimulates a cascade of intracellular signaling events to regulate stomatal movement. Analysis of the changes of cytosolic free Ca2+ ([Ca2+]cyt) and H2O2 in Vicia faba guard cells combined with epidermal strip bioassay suggests that ExtCaM induces an increase in both H2O2 levels and [Ca2+]cyt, leading to a reduction in stomatal aperture. Pharmacological studies implicate heterotrimeric G protein in transmitting the ExtCaM signal, acting upstream of [Ca2+]cyt elevation, and generating H2O2 in guard cell responses. To further test the role of heterotrimeric G protein in ExtCaM signaling in stomatal closure, we checked guard cell responses in the Arabidopsis (Arabidopsis thaliana) Galpha-subunit-null gpa1 mutants and cGalpha overexpression lines. We found that gpa1 mutants were insensitive to ExtCaM stimulation of stomatal closure, whereas cGalpha overexpression enhanced the guard cell response to ExtCaM. Furthermore, gpa1 mutants are impaired in ExtCaM induction of H2O2 generation in guard cells. Taken together, our results strongly suggest that ExtCaM activates an intracellular signaling pathway involving activation of a heterotrimeric G protein, H2O2 generation, and changes in [Ca2+]cyt in the regulation of stomatal movements.

Arabidopsis↗

PubMed2004

Apoptosis of murine melanoma B16-BL6 cells induced by quercetin targeting mitochondria, inhibiting expression of PKC-alpha and translocating PKC-delta.

PURPOSE: In our previous study, quercetin was found to induce apoptosis of murine melanoma B16-BL6 cells. The cellular and molecular mechanism of quercetin-induced apoptosis was investigated in the present study. METHODS: Nuclear morphology was determined by fluorescence microscopy. DNA fragmentation was analyzed by electrophoresis and quantified by the diphenylamine method. The transmembrane potential of mitochondria was measured by flow cytometry. Bcl-2, Bcl-X(L), PKC-alpha, PKC-beta, and PKC-delta were detected by Western blotting. Caspase activity was determined spectrophotometrically. RESULTS: Quercetin induced the condensation of nuclei of B16-BL6 cells in a dose-dependent pattern as visualized by Hoechst 33258 and propidium iodide dying. Phorbol 12-myristate 13-acetate (PMA), a PKC activator, significantly enhanced apoptosis induced by quercetin, while doxorubicin, a PKC inhibitor, markedly decreased it. Both PMA and doxorubicin showed a consistent effect on the fragmentation of nuclear DNA caused by various dosages of quercetin. Quercetin dose-dependently led to loss of the mitochondrial membrane potential, which was also significantly reinforced or antagonized by PMA and doxorubicin, respectively. Moreover, PMA showed reinforcement, while doxorubicin showed significant antagonization, of the quercetin-mediated decrease in the expression of Bcl-2. Quercetin promoted caspase-3 activity in a dose-dependent manner, which was also regulated by PMA and doxorubicin with a pattern similar to that seen in their effect on apoptosis, mitochondrial membrane potential and Bcl-2 expression, but none of these were directly affected by PMA and doxorubicin. Free fatty acid and chlorpromazine, a PKC activator and inhibitor, respectively, did not interfere with these effects of quercetin. B16-BL6 cells expressed PKC-alpha, PKC-beta, and PKC-delta. Quercetin dose-dependently inhibited the expression of PKC-alpha but not that of PKC-beta and PKC-delta. Doxorubicin almost completely blocked the effect of quercetin on the expression of PKC-alpha. Quercetin was also involved in the translocation of PKC-delta from the cytosol to the nucleus. PMA enhanced the effect of quercetin on the translocation of PKC-delta. CONCLUSIONS: These results indicate that quercetin induced apoptosis of murine melanoma B16-BL6 cells by injuring their mitochondria, increasing the activity of caspase-3, inhibiting the expression of Bcl-2 and PKC-alpha, and inducing the translocation of PKC-delta. Doxorubicin inhibited these effects of quercetin by blocking the decreased expression of PKC-alpha induced by quercetin while PMA increased these effects by enhancing the translocation of PKC-delta induced by quercetin.

Animals↗

PubMed2004

Identification and characterization of Bacillus anthracis by multiplex PCR on DNA chip.

Bacillus anthracis can be identified by detecting virulence factor genes located on two plasmids, pXO1 and pXO2. Combining multiplex PCR with arrayed anchored primer PCR and biotin-avidin alkaline phosphatase indicator system, we developed a qualitative DNA chip method for characterization of B. anthracis, and simultaneous confirmation of the species identity independent of plasmid contents. The assay amplifies pag gene (in pXO1), cap gene (in pXO2) and Ba813 gene (a B. anthracis specific chromosomal marker), and the results were indicated by an easy-to-read profile based on the color reaction of alkaline phosphatase. About 1 pg of specific DNA fragments on the chip wells could be detected after PCR. With the proposed method, the avirulent (pXO1+/2-, pXO1-/2+ and pXO1-/2-) strains of B. anthracis and distinguished 'anthrax-like' strains from other B. cereus group bacteria were unambiguously identified, while the genera other than Bacillus gave no positive signal.

Alkaline Phosphatase↗

PubMed2004

Electrochemical study of the XNA on Gold microarray.

A novel electrode array was developed based on the XNA on Gold trade mark microarray platform. The platform combines self-assembling monolayers, thick film patterning and streptavidin based immobilization to provide a robust, versatile platform capable of analysing virtually any biomolecule including nucleic acids, proteins, carbohydrates and lipids. Electrochemical analysis of the self-assembling monolayer/streptavidin (SAMS) XNA on Gold coating revealed that the ferrocene redox current for the SAMS modified electrode was greater than that with a bare Gold electrode. The electrochemical reaction of K4Fe(CN)6 was inhibited by the SAMS coating, but was reactivated upon addition of ferrocene. These results indicate that ferrocene is involved as a mediator in the electron transfer of K4Fe(CN)6 to the SAMS modified electrode. Addition of DNA to the SAMS resulted in only a minor change in the electrochemical signal, indicating that XNA on Gold can be used for electrochemical based bioanalysis. After cycling a SAMS electrode 50 times, no signs of deterioration were detected showing that coating has excellent stability. In addition to the biosensing applications, the scheme provides a non-invasive method for accessing the quality of the SAMS coatings which is of industrial interest. These studies show that the XNA on Gold microarray platform can be used for electrochemical studies, thus providing an additional alternative for developing multianalyte biosensors as well as expanding the range of detection methods available for microarray analysis.

DNA↗

PubMed2004

Human acyl-coenzyme A:cholesterol acyltransferase 1 (acat1) sequences located in two different chromosomes (7 and 1) are required to produce a novel ACAT1 isoenzyme with additional sequence at the N terminus.

A rare form of human ACAT1 mRNA, containing the optional long 5'-untranslated region, is produced as a 4.3-kelonucleotide chimeric mRNA through a novel interchromosomal trans-splicing of two discontinuous RNAs transcribed from chromosomes 1 and 7. To investigate its function, we express the chimeric ACAT1 mRNA in Chinese hamster ovary cells and show that it can produce a larger ACAT1 protein, with an apparent molecular mass of 56 kDa on SDS-PAGE, in addition to the normal, 50-kDa ACAT1 protein, which is produced from the ACAT1 mRNAs without the optional long 5'-untranslated repeat. To produce the 56-kDa ACAT1, acat1 sequences located at both chromosomes 7 and 1 are required. The 56-kDa ACAT1 can be recognized by specific antibodies prepared against the predicted additional amino acid sequence located upstream of the N-terminal of the ACAT1(ORF). The translation initiation codon for the 56-kDa protein is GGC, which encodes for glycine, as deduced by mutation analysis and mass spectrometry. Similar to the 50-kDa protein, when expressed alone, the 56-kDa ACAT1 is located in the endoplasmic reticulum and is enzymatically active. The 56-kDa ACAT1 is present in native human cells, including human monocyte-derived macrophages. Our current results show that the function of the chimeric ACAT1 mRNA is to increase the ACAT enzyme diversity by producing a novel isoenzyme. To our knowledge, our result provides the first mammalian example that a trans-spliced mRNA produces a functional protein.

Amino Acid Sequence↗

PubMed2004

Mobile ambipolar domain in carbon-nanotube infrared emitters.

We spatially resolve the infrared light emission from ambipolar carbon-nanotube field-effect transistors with long-channel lengths. Electrons and holes are injected from opposite contacts into a single nanotube molecule. The ambipolar domain, where electron and hole currents overlap, forms a microscopic light emitter within the carbon nanotube. We can control its location by varying gate and drain voltages. At high electric fields, additional stationary spots appear due to defect-assisted Zener tunneling or impact ionization. The laterally resolved measurement provides valuable insight into the transistor behavior, complementary to electronic device characteristics.

Journal Article↗

PubMed2004

Polymorphisms in the one-carbon metabolic pathway, plasma folate levels and colorectal cancer in a prospective study.

One-carbon (e.g., folate) metabolism plays a pivotal role in the etiology of colorectal cancer (CRC). Cytosolic serine hydroxymethyltransferase (cSHMT), methylenetetrahydrofolate dehydrogenase (MTHFD1) and glutamate carboxypeptidase II (GCPII) are key genes involved in this pathway. Several new polymorphisms have been identified and there is evidence implicating their functionality. We examined whether polymorphisms in these genes, i.e., cSHMT L474F, MTHFD1 R653Q and GCPII H475Y, modify the risk of CRC in the prospective Physicians' Health Study. Among the 270 incident CRC cases and 453 controls, none of the one-carbon polymorphisms were associated with risk of CRC. Compared to the wild-type genotype, the multivariate-adjusted relative risks and 95% confidence intervals were 1.14 [0.68, 1.93] for cSHMT 474FF, 1.04 [0.67, 1.62] for MTHFD1 653QQ and 1.00 [0.55, 1.82] for GCPII 474HY. Furthermore, we examined the associations between one-carbon polymorphisms and folate status in terms of plasma folate and homocysteine levels in this population. No independent gene effect was observed. Although compound homozygous variants at cSHMT and MTHFD1 loci had the lowest plasma folate levels compared to other compound genotypes, no significant gene-gene interactions were observed. Findings from our prospective investigation indicate that these newly identified polymorphisms in one-carbon metabolizing genes have limited functionality in modifying folate status and related CRC risk.

Adult↗

PubMed2004

[Effects of sustained release morphine hydrochloride tablets in management of cancer pain: a survey of 567 patients].

OBJECTIVE: To evaluate the effect and adverse effects of morphine hydrochloric sustained release for patients with cancer pain. METHODS: A total of 567 patients, 369 males (65.1%) and 198 females (34.9%), aged 65 - 90 with a mean age of 72.6, with cancer pain, 67.4% with severe pain, 28.2% with moderate pain, a and 4.4% with mild pain, that were treated in 25 hospitals from 13 provinces received oral morphine hydrochloric sustained release. The recommended initial dosage was 30 mg every 12 hours, and then the dosage was regulated according to the effects until the ideal anesthesia was achieved. All patients were asked to record the attacks of pain, quality of life, and any side effect of the treatment. RESULTS: The baseline mean pain intensity (NRS) was 7.0 +/- 1.8. On the day 1, 5, 10, 15, 20, 25 and 30, the mean pain scores were decreased to 4.6 +/- 2.6, 2.8 +/- 1.8, 2.7 +/- 1.8, 2.6 +/- 1.7, 2.5 +/- 1.6, 2.3 +/- 1.4, and 2.2 +/- 1.4 respectively (all P = 0.000). The general effective rate on day 30 was 89.8%. The mean dosages were 66 +/- 56 mg/d initially, 84 +/- 64 mg/d (10 - 800 mg/d) on day 15, and 92 +/- 67 mg/d (10 - 800 mg/d) on day 30. On the day 30, 55.1% of the patients received a dosage or= 241 mg/d. Ninety-one point six percent (89.4% - 95.8%) of the patients took morphine orally twice daily. The poor quality of life rate in the patients was 90.5% before treatment, and were 56.8% and 49.6% respectively on the day 15 and day 30 (P = 0.0000 and P = 0.0009). The incidence of side effects was 35.6% on day 1, and 15.1% on day 30. The common side effects were constipation (14.3%), nausea (13.4%), dizziness (3.4%), vomiting (2.8%), drowsiness (0.7%), dysuria (0.4%), mental symptoms (0.2%), and respiratory depression (0.2%). Sixty-eight point four percent of the patients preferred continuation of sustained release morphine hydrochloride treatment. CONCLUSION: Oral treatment with sustained release morphine hydrochloride for patients with cancer pain is effective, safe, and convenient, and can improve the quality of life. Sustained release morphine hydrochloride is worth recommending as a first-line drug for the treatment of patients with moderate to severe cancer pain, and the usually dosage is 120 mg or less per day.

Adolescent↗

PubMed2004

Identification of tumor-associated proteins in oral tongue squamous cell carcinoma by proteomics.

Oral tongue carcinoma is an aggressive tumor that particularly affects chronic smokers, drinkers and betel squid chewers. Patients often present symptoms at a late stage, and there is a high recurrence rate after treatment. In this article, we report the first proteomic analysis of oral tongue carcinoma to globally search for tumor related proteins. Apart from helping us to understand the molecular pathogenesis of the carcinoma, these proteins may also have potential clinical applications as biomarkers, enabling the tumor to be identified at an early stage in high risk individuals, treatment response to be predicted, and residual or recurrent carcinoma to be detected sooner after treatment. The protein expression profiles of ten oral tongue squamous cell carcinomas and their matched normal mucosal resection margins were examined by two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectroscopy. A number of tumor-associated proteins including heat shock protein (HSP)60, HSP27, alpha B-crystalline, ATP synthase beta, calgranulin B, myosin, tropomyosin and galectin 1 were consistently found to be significantly altered in their expression levels in tongue carcinoma tissues, compared with their paired normal mucosae. The expression profile portrays a global protein alteration that appears specific to oral tongue cancer. The potential of utilizing these tumor related proteins for screening cancer and monitoring recurrence warrants further investigation.

Adult↗

PubMed2004

Proteomics of buccal squamous cell carcinoma: the involvement of multiple pathways in tumorigenesis.

Squamous cell carcinoma (SCC) of the buccal mucosa is an aggressive oral cancer. It mainly occurs in Central and Southeast Asia, and is closely related to the practice of tobacco smoking and betel squid chewing. The high recurrence and low survival rates of buccal SCC require our continued efforts to understand the pathogenesis of the disease for designing better therapeutic strategies. We used proteomic technology to analyze buccal SCC tissues aiming at identifying tumor-associated proteins for the utilization as biomarkers or molecular targets. With the exception of alpha B-crystallin being substantially reduced, a number of proteins were found to be significantly over-expressed in cancer tissues. These increased proteins included glycolytic enzymes, heat-shock proteins, tumor antigens, cytoskeleton proteins, enzymes involved in detoxification and anti-oxidation systems, and proteins involved in mitochondrial and intracellular signaling pathways. These extensive protein variations indicate that multiple cellular pathways were involved in the process of tumorigenesis, and suggest that multiple protein molecules should be simultaneously targeted as an effective strategy to counter the disease. At least, SCC antigen, G protein, glutathione S-transferase, manganese superoxide dismutase, annexins, voltage-dependent anion channel, cyclophilin A, stratifin and galectin 7 are candidates for targeted proteins. The present findings also demonstrated that rich protein information can be produced by means of proteomic analysis for a better understanding of the oncogenesis and pathogenesis in a global way, which in turn is a basis for the rational designs of diagnostic and therapeutic methods.

Aged↗

PubMed2004

Tomato stress-responsive factor TSRF1 interacts with ethylene responsive element GCC box and regulates pathogen resistance to Ralstonia solanacearum.

Ethylene responsive factors (ERFs) are important in regulating plant pathogen resistance, abiotic stress tolerance and plant development. Recent studies have greatly enlarged the ERF protein family and revealed more important roles of ERFs in plants. Here, we report our finding of a tomato ERF protein TSRF1, which is transcriptionally up-regulated by ethylene, salicylic acid, or Ralstonia solanacearum strain BJ1057 infection. Biochemical analysis indicates that TSRF1 specifically interacts in vitro with the GCC box, an element present in the promoters of many pathogenesis-related (PR) genes. Further investigation evidences that TSRF1 activates in vivo the expression of reporter beta-glucuronidase gene controlled by GCC box. More importantly, overexpressing TSRF1 in tobacco and tomato constitutively activates the expression of PR genes, and subsequently enhancing transgenic plant resistance to the bacterial wilt caused by Ralstonia solanacearum strain BJ1057. Therefore our investigation not only extends the functions of ERF proteins in plant resistance to R. solanacearum, but also provides further clues to understanding the mechanism of host regulatory proteins in response to the infection of pathogens.

Amino Acid Sequence↗

PubMed2004

Enhancement of human ACAT1 gene expression to promote the macrophage-derived foam cell formation by dexamethasone.

In macrophages, the accumulation of cholesteryl esters synthesized by the activated acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) results in the foam cell formation, a hallmark of early atherosclerotic lesions. In this study, with the treatment of a glucocorticoid hormone dexamethasone (Dex), lipid staining results clearly showed the large accumulation of lipid droplets containing cholesteryl esters in THP-1-derived macrophages exposed to lower concentration of the oxidized low-density lipoprotein (ox-LDL). More notably, when treated together with specific anti-ACAT inhibitors, the abundant cholesteryl ester accumulation was markedly diminished in THP-1-derived macrophages, confirming that ACAT is the key enzyme responsible for intracellular cholesteryl ester synthesis. RT-PCR and Western blot results indicated that Dex caused up-regulation of human ACAT1 expression at both the mRNA and protein levels in THP-1 and THP-1-derived macrophages. The luciferase activity assay demonstrated that Dex could enhance the activity of human ACAT1 gene P1 promoter, a major factor leading to the ACAT1 activation, in a cell-specific manner. Further experimental evidences showed that a glucocorticoid response element (GRE) located within human ACAT1 gene P1 promoter to response to the elevation of human ACAT1 gene expression by Dex could be functionally bound with glucocorticoid receptor (GR) proteins. These data supported the hypothesis that the clinical treatment with Dex, which increased the incidence of atherosclerosis, may in part due to enhancing the ACAT1 expression to promote the accumulation of cholesteryl esters during the macrophage-derived foam cell formation, an early stage of atherosclerosis.

Arteriosclerosis↗

PubMed2004

Depolymerization of actin cytoskeleton is involved in stomatal closure-induced by extracellular calmodulin in Arabidopsis.

Extracellular calmodulin (CaM) plays significant roles in many physiological processes, but little is known about its mechanism of regulating stomatal movements. In this paper, whether CaM exists in the guard cell walls of Arabidopsis and whether depolymerization of actin cytoskeleton is involved in extracellular CaM-induced stomatal closing are investigated. It is found that CaM exists in guard cell walls of Arabidopsis, and its molecular weight is about 17 kD. Bioassay using CaM antagonists W7-agarose and anti-CaM serum shows that the endogenous extracellular CaM promotes stomatal closure and delays stomatal opening. The long radial actin filaments in guard cells undergo disruption in a time-dependent manner during exogenous CaM-induced stomatal closing. Pharmacological experiments show that depolymerization of actin cytoskeleton enhances the effect of exogenous CaM-induced stomatal closing and polymerization reduces the effect. We also find that exogenous CaM triggers an increase in [Ca2+]cyt of guard cells. If [Ca2+]cyt increase is blocked with EGTA, exogenous CaM-induced stomatal closure is inhibited. These results indicate that extracellular CaM causes elevation of [Ca2+]cyt in guard cells, subsequently resulting in disruption of actin filaments and finally leading to guard cells closure.

Actins↗