Biomedical subjects

Hong Qing

Publications and source records attributed to Hong Qing.

10 recordsLinked to original sources

PubMed2006

Real-time TaqMan polymerase chain reaction assays for quantitative detection and differentiation of Ureaplasma urealyticum and Ureaplasma parvum.

Evidence has been presented that the species currently known as Ureaplasma urealyticum should be separated into 2 species-Ureaplasma parvum (previously, U. urealyticum biovar 1) and U. urealyticum (previously, U. urealyticum biovar 2). Differentiation and quantification of U. parvum and U. urealyticum can provide important information of the epidemiology of Ureaplasma infections. We developed 2 real-time TaqMan polymerase chain reaction (PCR) assays that would allow rapid, specific, sensitive, quantitative detection and convenient differentiation of U. parvum and U. urealyticum. One hundred twenty-eight clinical specimens were studied and compared with results obtained by culture methods and conventional PCR. The positive rate of real-time TaqMan PCR (59.4%, 76 of 128) was higher than that of culture methods (42.2%, 54 of 128) and conventional PCR (50%, 64 of 128). Of 76 positive specimens, 86.8% (66) contained U. parvum only, 10.5% (8) contained U. urealyticum only, and 2.6% (2) contained both. The copy numbers of 11 positive specimens were in the range of 10(1) to 10(3) copies per reaction mixture, 18 in the range of 10(3) to 10(5), and 47 in the range of 10(5) to 10(8). In the future, quantitative detection and convenient differentiation of real-time TaqMan PCR assays will assist in the study of the pathogenesis and epidemiology of Ureaplasma infections.

Bacterial Typing Techniques↗

PubMed2006

Hypoxia facilitates Alzheimer's disease pathogenesis by up-regulating BACE1 gene expression.

The molecular mechanism underlying the pathogenesis of the majority of cases of sporadic Alzheimer's disease (AD) is unknown. A history of stroke was found to be associated with development of some AD cases, especially in the presence of vascular risk factors. Reduced cerebral perfusion is a common vascular component among AD risk factors, and hypoxia is a direct consequence of hypoperfusion. Previously we showed that expression of the beta-site beta-amyloid precursor protein (APP) cleavage enzyme 1 (BACE1) gene BACE1 is tightly controlled at both the transcriptional and translational levels and that increased BACE1 maturation contributes to the AD pathogenesis in Down's syndrome. Here we have identified a functional hypoxia-responsive element in the BACE1 gene promoter. Hypoxia up-regulated beta-secretase cleavage of APP and amyloid-beta protein (Abeta) production by increasing BACE1 gene transcription and expression both in vitro and in vivo. Hypoxia treatment markedly increased Abeta deposition and neuritic plaque formation and potentiated the memory deficit in Swedish mutant APP transgenic mice. Taken together, our results clearly demonstrate that hypoxia can facilitate AD pathogenesis, and they provide a molecular mechanism linking vascular factors to AD. Our study suggests that interventions to improve cerebral perfusion may benefit AD patients.

Alzheimer Disease↗

PubMed2006

Ubiquitin-proteasome pathway mediates degradation of APH-1.

Gamma-secretase catalyzes intramembraneous proteolysis of several type I transmembrane proteins, including beta-amyloid precursor protein (APP), to generate amyloid beta protein (Abeta), a key player in the pathogenesis of Alzheimer's disease (AD). The critical components of the gamma-secretase complex include presenilin (PS), nicastrin (NCT), presenilin enhancer-2 (PEN-2) and anterior pharynx defective-1 (APH-1). Abnormalities of the ubiquitin-proteasome pathway have been implicated in the pathogenesis of AD; while PS and PEN-2 turnover is regulated by this pathway, it is unknown whether the ubiquitin-proteasome pathway is also involved in the degradation of APH-1 protein. In this study, we found that the expression of endogenous and exogenous APH-1 significantly increased in cells treated with proteasome-specific inhibitors. The effect of the proteasome inhibitors on APH-1 was dose- and time-dependent. APH-1 protein was ubiquitinated. Pulse-chase metabolic labeling experiments showed that the degradation of newly synthesized radiolabeled APH-1 proteins was inhibited by lactacystin. Disruption of the PS1 and PS2 genes did not affect the degradation of APH-1 by the ubiquitin-proteasome pathway. Furthermore, over-expression of APH-1 and inhibition of proteasomal APH-1 degradation facilitated gamma-secretase cleavage of APP to generate Abeta. These results demonstrate that the degradation of APH-1 protein is mediated by the ubiquitin-proteasome pathway.

Acetylcysteine↗

PubMed2006

Increased BACE1 maturation contributes to the pathogenesis of Alzheimer's disease in Down syndrome.

Almost all Down syndrome (DS) patients develop characteristic Alzheimer's disease (AD) neuropathology, including neuritic plaques and neurofibrillary tangles, after middle age. The mechanism underlying AD neuropathology in DS has been unknown. Abeta is the central component of neuritic plaques and is generated from APP by cleavage by the beta- and gamma-secretases. Here we show that beta-secretase activity is markedly elevated in DS. The ratio of mature to immature forms of BACE1 is altered in DS. DS has significantly higher levels of mature BACE1 proteins in Golgi than normal controls. Time-lapse live image analysis showed that BACE1 proteins were predominantly immobile in Golgi in DS cells, while they underwent normal trafficking in controls. Thus, overproduction of Abeta in DS is caused by abnormal BACE1 protein trafficking and maturation. Our results provide a novel molecular mechanism by which AD develops in DS and support the therapeutic potential of inhibiting BACE1 in AD and DS.

Alzheimer Disease↗

PubMed2005

Distinct transcriptional regulation and function of the human BACE2 and BACE1 genes.

Amyloid beta protein (Abeta) is the principal component of neuritic plaques in Alzheimer's disease (AD). Abeta is derived from beta amyloid precursor protein (APP) by beta- and gamma-secretases. Beta-site APP cleaving enzyme 1 (BACE1) has been identified as the major beta-secretase. BACE2 is the homolog of BACE1. The BACE2 gene is on chromosome 21 and has been implicated in the pathogenesis of AD. However, the function of BACE2 in Abeta generation is controversial. Some studies have shown that BACE2 cleaved APP at the beta-site whereas other studies showed it cleaved around the alpha-secretase site. To elucidate the involvement of BACE2 in AD pathogenesis, we compared BACE2 and BACE1 gene regulation and their functions in Abeta generation. We cloned and functionally characterized the human BACE2 promoter. The BACE2 gene is controlled by a TATA-less promoter. Though Sp1 can regulate both BACE1 and BACE2 genes, comparative sequence analysis and transcription factor prediction showed little similarity between the two promoters. BACE1 increased APP cleavage at the beta-site and Abeta production whereas BACE2 did not. Overexpression of BACE2 significantly increased sAPP levels in conditioned media but markedly reduced Abeta production. Knockdown of BACE2 resulted in increased APP C83. Our data indicate that despite being homologous in amino acid sequence, BACE2 and BACE1 have distinct functions and transcriptional regulation. BACE2 is not a beta-secretase, but processes APP within the Abeta domain at a site downstream of the alpha-secretase cleavage site. Our data argue against BACE2 being involved in the formation of neuritic plaques in AD.

Alzheimer Disease↗

PubMed2004

Degradation of BACE by the ubiquitin-proteasome pathway.

The amyloid beta protein (Abeta) is derived from beta-amyloid precursor protein (APP). Cleavage of APP by beta-secretase generates a C-terminal fragment (APPCTFbeta or C99), which is subsequently cleaved by gamma-secretase to produce Abeta. BACE (or BACE1), the major beta-secretase involved in cleaving APP, has been identified as a Type 1 membrane-associated aspartyl protease. In this study, we found that treatment with proteasome inhibitors resulted in an increase in APP C99 levels, suggesting that APP processing at the beta-secretase site may be affected by the ubiquitin-proteasome pathway. To investigate whether the degradation of BACE is mediated by the proteasome pathway, cells stably transfected with BACE were treated with lactacystin. We found that BACE protein degradation was inhibited by lactacystin in a time- and dose-dependent manner. Non-proteasome protease inhibitors had no effect on BACE degradation. BACE protein is ubiquitinated. Furthermore, lactacystin increased APP C99 production and Abeta generation. Our data demonstrate that the degradation of BACE proteins and APP processing are regulated by the ubiquitin-proteasome pathway.

Acetylcysteine↗

PubMed2004

Transcriptional regulation of BACE1, the beta-amyloid precursor protein beta-secretase, by Sp1.

Proteolytic processing of the beta-amyloid precursor protein (APP) at the beta site is essential to generate Abeta. BACE1, the major beta-secretase involved in cleaving APP, has been identified as a type 1 membrane-associated aspartyl protease. We have cloned a 2.1-kb fragment upstream of the human BACE1 gene and identified key regions necessary for promoter activity. BACE1 gene expression is controlled by a TATA-less promoter. The region of bp -619 to +46 is the minimal promoter to control the transcription of the BACE1 gene. Several putative cis-acting elements, such as a GC box, HSF-1, a PU box, AP1, AP2, and lymphokine response element, are found in the 5' flanking region of the BACE1 gene. Transcriptional activation and gel shift assays demonstrated that the BACE1 promoter contains a functional Sp1 response element, and overexpression of the transcription factor Sp1 potentiates BACE gene expression and APP processing to generate Abeta. Furthermore, Sp1 knockout reduced BACE1 expression. These results suggest that BACE1 gene expression is tightly regulated at the transcriptional level and that the transcription factor Sp1 plays an important role in regulation of BACE1 to process APP generating Abeta in Alzheimer's disease.

Alzheimer Disease↗

PubMed2004

BACE1 gene expression and protein degradation.

Deposition of amyloid beta protein in the brain is the major pathological feature of Alzheimer's disease. Amyloid beta protein is generated from beta-amyloid precursor protein by beta-secretase and gamma-secretase. Proteolytic processing of amyloid precursor protein at the beta site by BACE1 is essential to generate amyloid beta protein. BACE1, the major beta-secretase involved in cleaving amyloid precursor protein, has been identified as a type 1 membrane-associated aspartyl protease. In this study, we found that BACE1 gene expression is controlled by a TATA-less promoter. BACE1 gene expression is tightly regulated at the transcriptional level and the transcription factor Sp1 plays an important role in regulation of BACE1 to process amyloid precursor protein generating amyloid beta protein. Furthermore, we found that BACE1 protein is ubiquitinated, and the degradation of BACE1 proteins and amyloid precursor protein processing are regulated by the ubiquitin-proteasome pathway.

Acetylcysteine↗

PubMed2003

The ability of atypical antipsychotic drugs vs. haloperidol to protect PC12 cells against MPP+-induced apoptosis.

The present study examined the effects of the atypical antipsychotic drugs clozapine, olanzapine, quetiapine and risperidone, on N-methyl-4-phenylpyridinium ion-induced apoptosis and DNA damage in PC12 cells, and explored the molecular mechanisms underlying these effects. Haloperidol, a typical antipsychotic drug, was used for comparison. Exposure of PC12 cells to 50 micro m N-methyl-4-phenylpyridinium ion for 24 h resulted in a 35-45% loss of cells in culture. Pretreatment with the aforementioned atypical antipsychotic drugs significantly reduced the N-methyl-4-phenylpyridinium ion-induced cell loss, whereas haloperidol (10-100 micro m) did not have this protective effect. Hoechst 33258 staining revealed the apoptotic nuclear features of the N-methyl-4-phenylpyridinium ion-induced cell death, and showed that the atypical antipsychotic drugs, but not haloperidol, effectively prevented PC12 cells from this N-methyl-4-phenylpyridinium ion-induced apoptosis. DNA fragmentation assays further confirmed the N-methyl-4-phenylpyridinium ion-induced nuclear fragmentation. Pretreatment with the atypical antipsychotic drugs completely prevented this nuclear fragmentation, whereas haloperidol only partially prevented it. In vitro oligonucleotide assays indicated an activation of a specific glycosylase that recognizes and cleaves bases (at the 8-hydroxyl-2-deoxyguanine site) that were damaged by N-methyl-4-phenylpyridinium ion. Pretreatment with the atypical antipsychotic drugs more effectively attenuated this N-methyl-4-phenylpyridinium ion-induced activation than did haloperidol. Northern blot analyses showed that the atypical antipsychotic drugs, but not haloperidol, blocked the N-methyl-4-phenylpyridinium ion-induced substantial increase of copper/zinc superoxide dismutase mRNA in PC12 cells. Atypical antipsychotic drugs slightly up-regulated the expression of copper/zinc superoxide dismutase mRNA, whereas haloperidol strongly increased the expression of copper/zinc superoxide dismutase mRNA. These data may account for the different therapeutic effects and side-effect profiles of typical and atypical antipsychotic drugs in schizophrenia.

1-Methyl-4-phenylpyridinium↗

PubMed2002

Quetiapine attenuates the immobilization stress-induced decrease of brain-derived neurotrophic factor expression in rat hippocampus.

Quetiapine is a new atypical antipsychotic drug widely used in the treatment of schizophrenia and other psychotic disorders. This study examined the influence of quetiapine on the decrease of brain-derived neurotrophic factor (BDNF) expression, induced by chronic immobilization stress, in the hippocampus of the rat. Pretreatment with 10 mg/kg of quetiapine markedly attenuated the stress-induced decrease in levels of BDNF protein, as determined by Western blot analyses, and the reduction of BDNF immunoreactivity, in hippocampal pyramidal and dentate granular neurons. These results suggest that the chronic administration of quetiapine could be neuroprotective to hippocampal neurons in schizophrenia and this effect may be related to its antipsychotic effect in patients with schizophrenia.

Animals↗