Lifen Yao

Cardiovascular disease contributes to Alzheimer's disease: evidence from large-scale genome-wide association studies

Alzheimers disease (AD) is the most common and complex neurodegenerative disease in the elderly individuals. Recently, genome-wide association studies (GWAS) have been used to investigate AD pathogenesis. These GWAS have yielded important new insights into the genetic mechanisms of AD. However, these newly identified AD susceptibility loci exert only very small risk effects and cannot fully explain the underlying AD genetic risk. We hypothesize that combining the findings from different AD GWAS may have greater power than genetic analysis alone. To identify new AD risk factors, we integrated findings from 3 previous large-scale AD GWAS (n = 14,138) using a gene-based meta-analysis and subsequently conducted a pathway analysis using the kyoto encyclopedia of genes and genomes and gene ontology databases. Interestingly, we not only confirmed previous findings, but also highlighted, for the first time, the involvement of cardiovascular disease-related pathways in AD. Our results provided the clues as to the link between these diseases using pathway analysis methods. We believe that these findings will be very useful for future genetic studies of AD.

TCTP promotes glioma cell proliferation in vitro and in vivo via enhanced β-catenin/TCF-4 transcription

Background The translationally controlled tumor protein (TCTP) is a multifunctional protein that plays important roles in immune responses, cell proliferation, tumorigenicity and cell apoptosis. Here, we examined the clinical value of TCTP in glioma patient survival and investigated the functional roles and mechanism of TCTP in glioma development. Methods TCTP expression was determined through immunohistochemical staining, immunoblotting, and quantitative real-time PCR (qRT-PCR). TCTP or TCF-4 expression was silenced using short hairpin (sh) RNA. In vitro cell proliferation was detected using MTT, BrdU and colony formation assays, and in vivo tumor growth was performed using the xenograft model. TCTP/TCF-4/β-catenin association was detected using a co-immunoprecipitation (co-IP) assay. TCF-4 transcription activity was detected using a TOPflash/FOPflash report gene assay. Wnt/β-catenin-targeted gene expression was detected through Western blotting. Results TCTP protein levels were significantly elevated in high-grade gliomas compared with low-grade gliomas and normal brain tissues. Importantly, the expression of TCTP was significantly associated with poorer overall survival and disease-free survival, and TCTP also reduced the survival rate after treatment with radiotherapy and temozolomide (RT-TMZ) for glioma patients. The ectopic expression of TCTP enhanced glioma cell proliferation both in vitro and in vivo, whereas the knockdown of TCTP inhibited this effect. Similarly, the overexpression of TCTP increased β-catenin binding to TCF-4, TOPflash report gene transcription activity, and the expression of Wnt/β-catenin signaling target genes including c-Myc and cyclin D1; notably, the knockdown of TCTP reduced these effects. The knockdown of TCF-4 using shRNA rescued the enhanced cell proliferation induced by the overexpression of TCTP. Conclusion TCTP is associated with reduced survival of glioma patients and induces glioma tumor growth through enhanced Wnt/β-catenin signaling.

Polymorphism −116C/G of Human X-box-Binding Protein 1 Promoter is Associated with Risk of Alzheimer's Disease

Alzheimers disease (AD) is a multifactor disease that has been reported to have a close association with endoplasmic reticulum (ER) stress response. In the response, the regulator factor human X‐box‐binding protein 1 (XBP1) has been shown to facilitate the refolding and degradation of misfolded proteins, prevent neurotoxicity of amyloid‐beta (Aβ) and tau, and play an important role in the survival of neurons. The aim in the study was to analyze the potential association between the −116C/G polymorphism of XBP1 and the risk of AD.

Interaction between Interleukin-8 and Methylenetetrahydrofolate Reductase Genes Modulates Alzheimer’s Disease Risk

Background/Aim: Interleukin-8 (IL-8), a potent chemoattractant for neutrophils, has been implicated in the pathogenesis of Alzheimer’s disease (AD). The ability of individuals to produce high levels of IL-8 is partially determined by the IL-8 –251 T/A polymorphism. Therefore, we investigated the association between this polymorphism and AD in a Chinese population. Additionally, in light of the stimulatory effect of homocysteine on the production of IL-8, we also sought to determine whether the methylenetetrahydrofolate reductase (MTHFR) gene 677 C/T variant, a genetic modifier of the serum homocysteine level, may interact with the IL-8 –251 polymorphism in determining the AD risk. Methods: Genotyping of 198 AD patients and 240 matched controls was performed by PCR-RFLP. Results: The presence of the MTHFR 677 C/T and 677 T/T genotypes conferred a marginally significant increase in the risk for AD (OR = 1.666, 95% CI = 1.022–2.715, and OR = 1.892, 95% CI = 1.124–3.187) and the presence of the IL-8 –251 polymorphism was not associated with AD. However, the OR for AD associated with joint occurrence of the MTHFR 677 T/T and the IL-8 –251 A/A genotypes was 2.512 (95% CI = 1.151–5.483). Conclusion: Our data suggest a critical role for IL-8/MTHFR interactions in the development of AD.

A functional p.82G>S polymorphism in the RAGE gene is associated with multiple sclerosis in the Chinese population

Background: The receptor for advanced glycation end products (RAGE) and its proinflammatory ligand, S100-calgranulins, are critically implicated in the pathological progression of multiple sclerosis (MS). A functional polymorphism within the V-type immunoglobulin domain of RAGE gene, p.82G>S (c.557G>A), has been shown to affect ligand binding affinity and thus may affect susceptibility to MS. Methods: The RAGE p.82G>S polymorphism was genotyped in 144 MS patients and 156 healthy controls using polymerase chain reaction – restriction fragment length polymorphism. A replication study was performed on a second cohort comprising 138 patients and 150 controls. The relationship between the RAGE p.82G>S polymorphism and circulating levels of soluble RAGE (sRAGE), a secreted decoy receptor against RAGE signaling, was also investigated. Results: In both initial and replication cohorts, an increased MS risk was detected in RAGE p.82G>S variant allele carriers (odds ratio [OR] = 1.786, p = 0.0134 and OR = 1.732, p = 0.0210, respectively). This association signal persisted in subgroups of women and patients with relapsing–remitting MS. Moreover, compared with the wild-type 82GG carriers, carriers of the variant allele presented a faster progression of disability and a reduced serum sRAGE level. Conclusions: The present study provides preliminary evidence that the gain-of-function p.82G>S polymorphism in the RAGE gene is associated with an increased risk of MS in the Chinese population.

Genetic Association of MiR-146a with Multiple Sclerosis Susceptibility in the Chinese Population

Background: miR-146a polymorphisms have been involved in susceptibility to multiple diseases. The aim of the present study was to analyze the potential association between two functional miR-146a polymorphisms (rs2910164 and rs57095329) and multiple sclerosis (MS) in the Han Chinese population. Methods: A cohort of 525 patients and 568 healthy controls were genotyped to detect the two polymorphisms by SNaPshot. Results: No significant differences were detected in the distribution of the two miR-146a polymorphisms between the patients and controls (P > 0.05). However, stratification by gender showed a statistically significant difference in the frequency of the genotype rs2910164 between MS patients and control females (P=0.009). Further stratification analysis by subgroup revealed that the miR-146a rs2910164 C allele conferred a higher risk of developing relapsing-remitting MS (RRMS) (P=0.018). In addition, the rs2910164 C allele was significantly associated with increased expression of miR-146a in patients with RRMS (P=0.025). Moreover, patients with the rs2910164 C allele released more TNF-α and IFN-γ, but not IL-1β, compared with individuals carrying the homozygous GG genotype (P < 0.05). Conclusions: Our results provide evidence that rs2910164 may play a role in MS susceptibility in females. The rs2910164 G>C variation may affect the expression of miR-146a and the release of proinflammatory cytokines.

Influence of the Pro12Ala polymorphism of PPAR-γ on age at onset and sRAGE levels in Alzheimer's disease

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) has been described to have a role in the modulation of various genes involved in Abeta homeostasis, inflammation, and energy metabolism, making it a candidate gene for risk of Alzheimers disease (AD). A functional polymorphism in exon 2 of the PPAR-gamma gene has been related to AD, but the effects are inconsistent across studies. To determine the role of PPAR-gamma in genetic susceptibility to AD in a representative Chinese sample, we genotyped 362 AD patients and 370 healthy controls for PPAR-gamma Pro12Ala polymorphism by polymerase chain reaction-restriction fragment length polymorphism method. We also examined the potential impact of this polymorphism on plasma level of soluble receptor for advanced glycation end products (sRAGE), a decoy receptor whose reduction has been associated with a higher risk of AD. Our results suggest that PPAR-gamma Pro12Ala polymorphism was not associated with an increased risk of AD in the overall sample. Stratification analysis revealed that the PPAR-gamma Pro/Ala genotype may be associated with the development of early-onset AD in the individuals without APOE epsilon4 allele (OR=3.76, 95% CI=1.10-12.84; p=0.03), but this association became insignificant after Bonferroni correction (p (corr)=0.10). Moreover, in the subgroup of APOE epsilon4 noncarriers, Kaplan-Meier survival analyses indicated that AD patients with the Pro/Ala genotype presented with disease onset 4.6 years earlier than carriers of Pro/Pro genotype. Further investigation revealed that AD patients carrying Pro/Ala genotype had significantly lower plasma sRAGE levels than patients with Pro/Pro genotype. These findings suggest that the functional PPAR-gamma Pro12Ala polymorphism may modify the age at onset of AD.

A functional polymorphism of the microRNA-146a gene is associated with susceptibility to drug-resistant epilepsy and seizures frequency.

PURPOSE Epilepsy is the third most common chronic brain disorder and is characterized by an enduring predisposition for seizures. Recently, a growing body of evidence has suggested that microRNA-146a (miR-146a) is upregulated in the brains of epilepsy patients and of mouse models; furthermore, miR-146a may be involved in the development and progression of seizures through the regulation of inflammation and immune responses. In this report, we performed a case-control study to analyze the relationship between the two potentially functional single nucleotide polymorphisms (SNPs) of the miR-146a gene (rs2910464 and rs57095329) and the risk of epilepsy in a Chinese population comprising 249 cases and 249 healthy controls. METHOD Our study comprised 249 epilepsy patients and 249 healthy controls in two regions of China. The DNA was genotyped using the ABI PRISM SNapShot method. The statistical analysis was estimated using the chi-square test or Fishers exact test. RESULTS Our results indicated a significant association between the rs57095329 SNP of the miR-146a gene and the risk of drug resistant epilepsy (DRE) (genotypes, p = 0.0258 and alleles, p = 0.0108). Moreover, the rs57095329 A allele was found to be associated with a reduced risk of seizures frequency in DRE patients (all p < 0.001). However, the rs2910164 variant was not associated with epilepsy. CONCLUSION Our data indicate that the rs57095329 polymorphism in the promoter region of miR-146a is involved in the genetic susceptibility to DRE and the seizures frequency.

Association between the macrophage inflammatory protein-l alpha gene polymorphism and Alzheimer's disease in the Chinese population

Genetic polymorphisms in chemokine receptor and their natural ligand genes have been shown to modify the disease progression of Alzheimers disease (AD). Human macrophage inflammatory protein-1 alpha (MIP-1alpha) is a chemotactic cytokine which plays a considerable role in AD pathogenesis, but its genetic contribution to AD has never been investigated. Recently, a biallelic dinucleotide microsatellite repeat (TA repeat) polymorphism has been found in the MIP-1alpha gene promoter region at position -906. We investigated whether this promoter polymorphism of MIP-1alpha gene might be responsible for susceptibility to AD in a Chinese population, utilizing a clinically well-defined group of 138 sporadic AD patients and 180 age-matched controls. We also examined the combined gene effects between the MIP-1alpha and apolipoprotein E (APOE) genes. The overall distribution of MIP-1alpha-906 alleles and genotypes was significantly different between AD cases and controls (P<0.05). The odds ratio for AD associated with the (TA)(6)/(TA)(6) versus non-(TA)(6)/(TA)(6) genotype was 1.893 (95% CI=1.208-2.967), while that for APOE varepsilon4 and MIP-1alpha (TA)(6)/(TA)(6) carriers was 7.140 (95% CI=3.222-15.823). In addition, we found that serum MIP-1alpha levels in patients with (TA)(6)/(TA)(6) genotype were increased significantly when compared with non-(TA)(6)/(TA)(6) genotype. The results indicate that the MIP-1alpha-906 (TA)(6)/(TA)(6) genotype, either by itself or interacting with the APOE varepsilon4 gene seems to be a genetic risk factor for AD. This genotype is associated with elevated serum MIP-1alpha levels in patients, which can contribute to increase the inflammatory process occurring in AD.

Identification of STC1 as an β-amyloid activated gene in human brain microvascular endothelial cells using cDNA microarray

To explore the molecular basis underlying beta-amyloid peptide (Abeta)-induced toxicity in the cerebrovasculature, we performed a cDNA microarray analysis to investigate the transcriptional profile induced by Abeta in human brain microvascular endothelial cells (HBMECs). This study identified 24 differentially expressed genes in HBMECs upon Abeta treatment. Among these genes, we found that the gene for a well-characterized calcium-regulating hormone, stanniocalcin-1 (STC1) was specifically up-regulated by Abeta treatment in a time and dose-dependent manner. Moreover, using overexpression and knock-down strategies, we found that overexpression of STC1 decreased transmigration of monocytes induced by Abeta and prevented Abeta-induced apoptosis of HBMECs. In addition, we explored the possible mechanisms underlying the effects of STC1, showing that overexpression of STC1 attenuated the effect of Abeta on up-regulating early growth response-1 (Egr-1), macrophage inflammatory protein-1beta (MIP-1beta), or cleaved caspase-8. Our data thus indicate a key role of STC1 in the response of HBMECs to Abeta exposure.