Computational insights into the substrate recognition mechanism of cartilage extracellular matrix degradation.

Articular cartilage is connective tissue that forms a slippery load-bearing joint surface between bones. With outstanding mechanical properties, it plays an essential role in cushioning impact and protecting the ends of bones. Abnormal mechanical stimulation, such as repetitive overloading or chondral injury, induces excessive cartilage extracellular matrix (ECM) degradation, leading to osteoarthritis and other joint disorders. A disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5) is an aggrecanase that dominates the catalysis of aggrecan, the major proteoglycan in the cartilage ECM. Intriguingly, unlike its critical cleavage site Glu373-374Ala, another potential cleavage site, Glu419-420Ala, composed of the same amino acids in the aggrecan interglobular domain, is not a major cleavage site. It remains unclear how ADAMTS-5 distinguishes between them and hydrolyzes the correct scissile bonds. This research introduces a bottom-up in silico approach to reveal the molecular mechanism by which ADAMTS-5 recognizes the cleavage site on aggrecan. It is hypothesized that the sequence in the vicinity assists ADAMTS-5 in positioning the cleavage site. Specific residues were found to serve as binding sites, helping aggrecan bind more stably and fit into the enzyme better. The findings provide insight into the substrate binding and recognition mechanism for cartilage ECM degradation from a brand new atomic-scale perspective, laying the foundation for prophylaxis and treatment of related joint diseases.

Management of low-density lipoprotein cholesterol levels in South Africa: the International ChoLesterol management Practice Study (ICLPS).

The International Cholesterol Management Practice Study (ICLPS) South Africa investigated achievement of European Society of Cardiology (ESC)/European Atherosclerosis Society (EAS) guideline low-density lipoprotein cholesterol (LDL-C) targets in real-world clinical practice. Demographic data, clinical characteristics, cardiovascular risk factors, lipid-modifying medications, lipid values and investigator's assessment of cardiovascular risk were recorded for 396 patients on stable lipid-modifying therapy. Most (98.7%) patients received statins; 25.1% of statin-treated patients were receiving high-intensity statins. Overall, 41.4% of patients achieved their LDL-C target; among 354 (89.4%) patients in whom cardiovascular disease risk, based on ESC Systematic Coronary Risk Estimation (SCORE) was calculated, achievement rate was 14.3% for moderate-risk (n = 7), 59.3% for high-risk (n = 123) and 32.3% for very high-risk patients (n = 223). Half of Asian (54.7%) and black African (53.2%) patients were at LDL-C target compared with 29.8% of European/Caucasian and 27.3% of 'other' patients. Improved guideline adherence and greater use of combination therapy may increase LDL-C goal achievement.

The Potential Regulatory Mechanisms of miR-196a in Huntington's Disease through Bioinformatic Analyses.

High throughput screening is a powerful tool to identify the potential candidate molecules involved during disease progression. However, analysis of complicated data is one of the most challenging steps on the way to obtaining useful results from this approach. Previously, we showed that a specific miRNA, miR-196a, could ameliorate the pathological phenotypes of Huntington's disease (HD) in different models, and performed high throughput screening by using the striatum of transgenic mice. In this study, we further tried to identify the potential regulatory mechanisms using different bioinformatic tools, including Database for Annotation, Visualization and Integrated Discovery (DAVID), Molecular Signatures Database (MSigDB), TargetScan and MetaCore. The results showed that miR-196a dominantly altered "ABC transporters", "RIG-I-like receptor signaling pathway", immune system", "adaptive immune system","tissue remodeling and wound repair" and "cytoskeleton remodeling". In addition, miR-196a also changed the expression of several well-defined pathways of HD, such as apoptosis and cell adhesion. Since these analyses showed the regulatory pathways are highly related to the modification of the cytoskeleton, we further confirmed that miR-196a could enhance the neurite outgrowth in neuroblastoma cells, suggesting miR-196a might provide beneficial functions through the alteration of cytoskeleton structures. Since impairment of the cytoskeleton has been reported in several neuronal diseases, this study will provide not only the potential working mechanisms of miR-196a but also insights for therapeutic strategies for use with different neuronal diseases.

von Hippel-Lindau gene plays a role during zebrafish pronephros development.

von Hippel-Lindau (pVHL)-mediated ubiquitination of HIF-1α plays a central role in the cellular responses to changes in oxygen availability. In the present study, using zebrafish as a model, we showed that specific knockdown of endogenous vhl leads to pronephros malformation and renal failure. Knockdown of vhl resulted in abnormal kidney development, including curved and cystic pronephric tubule or/and cystic and atrophic glomerulus. Co-injecting capped vhl messenger RNA (mRNA) partially rescued pronephros morphant phenotype, confirming the specificity of the morpholino oligonucleotide (MO)-induced pronephric defects. In keeping with the pronephros phenotype, renal function was affected as well in vhl morphants. Dextran clearance abilities of vhl morphants were significantly reduced as compared with those of control embryos. Further analysis indicated that glomerular integrity is impaired in vhl morphants, while the organization of pronephric duct was minimally affected. Vhl morphants display global increased vegf signaling and angiogenesis. In addition, we found that vhl morphants displayed elevated expression of vegfa in podocytes and increased angiogenesis at pronephric glomerulus and the nearby vessels. Treatment of vegf inducer to embryos also caused pronephros phenotype resembling vhl morphants, further supporting that increased vegfa signaling contribute to the pronephros morphant phenotype. Our study establishes the zebrafish as an alternative vertebrate model system for studying Vhl function during kidney development.

miR-196a ameliorates phenotypes of Huntington disease in cell, transgenic mouse, and induced pluripotent stem cell models.

Huntington disease (HD) is a dominantly inherited neurodegenerative disorder characterized by dysregulation of various genes. Recently, microRNAs (miRNAs) have been reported to be involved in this dysregulation, suggesting that manipulation of appropriate miRNA regulation may have a therapeutic benefit. Here, we report the beneficial effects of miR-196a (miR196a) on HD in cell, transgenic mouse models, and human induced pluripotent stem cells derived from one individual with HD (HD-iPSCs). In the in vitro results, a reduction of mutant HTT and pathological aggregates, accompanying the overexpression of miR-196a, was observed in HD models of human embryonic kidney cells and mouse neuroblastoma cells. In the in vivo model, HD transgenic mice overexpressing miR-196a revealed the suppression of mutant HTT in the brain and also showed improvements in neuropathological progression, such as decreases of nuclear, intranuclear, and neuropil aggregates and late-stage behavioral phenotypes. Most importantly, miR-196a also decreased HTT expression and pathological aggregates when HD-iPSCs were differentiated into the neuronal stage. Mechanisms of miR-196a in HD might be through the alteration of ubiquitin-proteasome systems, gliosis, cAMP response element-binding protein pathway, and several neuronal regulatory pathways in vivo. Taken together, these results show that manipulating miR-196a provides beneficial effects in HD, suggesting the potential therapeutical role of miR-196a in HD.

Suppression of dual-specificity phosphatase-2 by hypoxia increases chemoresistance and malignancy in human cancer cells.

Hypoxia inducible factor-1 (HIF-1) is the master transcriptional regulator of the cellular response to altered oxygen levels. HIF-1α protein is elevated in most solid tumors and contributes to poor disease outcome by promoting tumor progression, metastasis, and resistance to chemotherapy. To date, the relationship between HIF-1 and these processes, particularly chemoresistance, has remained largely unexplored. Here, we show that expression of the MAPK-specific phosphatase dual-specificity phosphatase-2 (DUSP2) is markedly reduced or completely absent in many human cancers and that its level of expression inversely correlates with that of HIF-1α and with cancer malignancy. Analysis of human cancer cell lines indicated that HIF-1α inhibited DUSP2 transcription, which resulted in prolonged phosphorylation of ERK and, hence, increased chemoresistance. Knockdown of DUSP2 increased drug resistance under normoxia, while forced expression of DUSP2 abolished hypoxia-induced chemoresistance. Further, reexpression of DUSP2 during cancer progression caused tumor regression and markedly increased drug sensitivity in mice xenografted with human tumor cell lines. Furthermore, a variety of genes involved in drug response, angiogenesis, cell survival, and apoptosis were found to be downregulated by DUSP2. Our results demonstrate that DUSP2 is a key downstream regulator of HIF-1-mediated tumor progression and chemoresistance. DUSP2 therefore may represent a novel drug target of particular relevance in tumors resistant to conventional chemotherapy.

DNA methylation of the Trip10 promoter accelerates mesenchymal stem cell lineage determination.

Epigenetic regulation of gene expression by DNA methylation and histone modification controls cell fate during development and homeostasis in adulthood. Aberrant epigenetic modifications may lead to abnormal development, even diseases. We have found that Trip10 (thyroid hormone receptor interactor 10), an adaptor protein involved in diverse functions, is epigenetically regulated during lineage-specific induction of human bone marrow-derived mesenchymal stem cells (MSCs). To determine whether DNA methylation-induced gene silencing is sufficient to restrict cell fate changes, we applied an invitro method to specifically methylate the promoter of Trip10. Our hypothesis was that the methylation status of the Trip10 promoter in MSCs alters the differentiation preference of MSCs. Transfection of in vitro-methylated Trip10 promoter DNA into MSCs resulted in progressive accumulation of cytosine methylation at the endogenous Trip10 promoter, reduced Trip10 expression, and accelerated MSC-to-neuron and MSC-to-osteocyte differentiation. A two-component EGFP reporter gene system was established to confirm the level of transcriptional silencing and visualize the targeted DNA methylation. EGFP expression induced in the reporter system by targeted Trip10 methylation was reversed by adding 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor, confirming that the suppressed Trip10 expression and disrupted MSC differentiation resulted from the in vitro-introduced methylations in the Trip10 promoter. With this targeted DNA methylation and reporter system, we are able to monitor the progression of locus-specific DNA methylation in vivo and correlate such changes with potential functional changes. Using this approach, we have established a new role for Trip10, showing that the level of Trip10 expression is associated with the maintenance and differentiation of MSCs.

Regulation of CD151 by hypoxia controls cell adhesion and metastasis in colorectal cancer.

PURPOSE: The first step of metastasis is the detachment of cancer cells from the surrounding matrix and neighboring cells; however, how cancer cells accomplish this process remains unclear. Thus, we aimed to investigate the underlying mechanism that controls the early event of metastasis. EXPERIMENTAL DESIGN: One hundred and thirty-seven paired colorectal carcinoma and normal colon tissues were examined by immunohistochemical staining and Western blot for the expression of CD151, a member of the tetraspanin family that plays important roles in cell adhesion and motility. The effect of CD151 on cancer cell adhesion was investigated under normoxia and hypoxia conditions. RESULTS: The level of CD151 was down-regulated in colon cancer compared with the paired normal counterparts. Expression of CD151 was negatively regulated by hypoxia inducible factor-1-dependent hypoxic stress. Suppression of CD151 by hypoxia caused the detachment of cancer cells from the surrounding matrix and neighboring cells whereas restoration of CD151 expression during reoxygenation facilitated the adhesion capacity. Clinical examination further showed that metastasized cancer cells expressed a greater level of CD151 compared with that of primary tumor. CONCLUSION: Regulation of CD151 by oxygen tension may play an important role in cancer metastasis by regulating the detachment from the primary site and homing in the secondary site.

Induction of pyruvate dehydrogenase kinase-3 by hypoxia-inducible factor-1 promotes metabolic switch and drug resistance.

The switch of cellular metabolism from mitochondrial respiration to glycolysis is the hallmark of cancer cells and associated with tumor malignancy. However, the mechanism of this metabolic switch remains largely unknown. Herein, we reported that hypoxia-inducible factor-1 (HIF-1) induced pyruvate dehydrogenase kinase-3 (PDK3) expression leading to inhibition of mitochondrial respiration. Promoter activity assay, small interference RNA knockdown assay, and chromatin immunoprecipitation assay demonstrated that hypoxia-induced PDK3 gene activity was regulated by HIF-1 at the transcriptional level. Forced expression of PDK3 in cancer cells resulted in increased lactic acid accumulation and drugs resistance, whereas knocking down PDK3 inhibited hypoxia-induced cytoplasmic glycolysis and cell survival. These data demonstrated that increased PDK3 expression due to elevated HIF-1alpha in cancer cells may play critical roles in metabolic switch during cancer progression and chemoresistance in cancer therapy.

Transcriptional repression of human cad gene by hypoxia inducible factor-1alpha.

De novo biosynthesis of pyrimidine nucleotides provides essential precursors for DNA synthesis and cell proliferation. The first three steps of de novo pyrimidine biosynthesis are catalyzed by a multifunctional enzyme known as CAD (carbamoyl phosphate synthetase-aspartate carbamoyltransferase-dihydroorotase). In this work, a decrease in CAD expression is detected in numerous cell lines and primary culture human stromal cells incubated under hypoxia or desferrioxamine (DFO)-induced HIF-1alpha accumulation. A putative hypoxia response element (HRE) binding matrix is identified by analyzing human cad-gene promoter using a bioinformatic approach. Promoter activity assays, using constructs harboring the cad promoter (-710/+122) and the -67/HRE fragment (25-bases), respectively, demonstrate the suppression of reporter-gene expression under hypoxia. Suppression of cad-promoter activity is substantiated by forced expression of wild-type HIF-1alpha but abolished by overexpression of dominant-negative HIF-1alpha. A chromatin immunoprecipitation assay provides further evidence that HIF-1alpha binds to the cad promoter in vivo. These data demonstrate that the cad-gene expression is repressed by HIF-1alpha, which represents a functional link between hypoxia and cell-cycle arrest.

Levamisole modulates prostaglandin E2 production and cyclooxygenase II gene expression in human colonic cancer cells.

BACKGROUND: Colorectal adenocarcinoma is one of the leading causes of cancer mortality in the world. Recent studies have demonstrated that prostaglandin E(2) (PGE(2)) and cyclooxygenase (COX) are involved in the early development of colorectal cancer. Levamisole together with 5-fluorouracil has been shown to improve the survival of patients with Duke's C colon cancer. This study examined the effect of levamisole on PGE(2) production and COX-2 gene activation in immortalized human colon cells. MATERIALS AND METHODS: Colon 205 cells, a human colonic cancer cell line, were exposed to Escherichia coli LPS (1 microg/mL) in the presence of levamisole (1 microm to 1 mm). The PGE(2) production was determined by enzyme-linked immunosorbent assay. In addition, cyclooxygenase II (COX-2) mRNA expression and COX-2 protein were measured by the real-time reverse transcription polymerase chain reaction and Western blot assay, respectively. Transcription factor nuclear factor (NF)-kappaB activity of the nuclear and cytoplasmic proteins was determined by Western blot assay with a P65 antibody. RESULTS: Colon 205 cells produced significantly more PGE(2) when stimulated by LPS. Levamisole inhibited PGE(2) production by LPS-stimulated colon 205 cells in a dose-dependent fashion. In addition, COX-2 mRNA expression and COX-2 protein induced by LPS were also reduced by levamisole. Finally, NF-kappaB activation of LPS-stimulated colon cells was inhibited by levamisole. CONCLUSION: Levamisole inhibits PGE(2) production by LPS-stimulated colon 205 cells. The inhibition of levamisole occurs at the transcription level of COX-2 gene and is regulated through NF-kappaB activation.

Longitudinal changes in craniofacial factors among snoring and nonsnoring Bolton-Brush study participants.

The extent to which craniofacial risk factors are manifested from childhood in habitual snorers and those with obstructive sleep apnea hypopnea syndrome (OSAHS) is unknown. The purpose of this study was to examine the differences in craniofacial factors between snorers and nonsnorers from childhood to adulthood. The sample consisted of 80 Bolton-Brush subjects (men, 52%; white, 100%) recalled at adult ages (53-78 years) who had existing prepubertal (age, 4-5 years) and pubertal (age, 12-13 years) records. Snoring was assessed at the adult age through subjective and spousal reports. Cephalometric radiographs were used to characterize 13 craniofacial hard and soft tissue measurements. The t tests revealed that there was a trend (P <.10) for longer hyoid-to-mandibular plane distance at prepubertal and pubertal ages and significant (P <.05) differences at adult recall for snorers. Posterior airway space was significantly smaller for snorers at adult recall. The longitudinal analysis did show a significant change in 9 craniofacial variables over time, but this change was not different between snorers and nonsnorers. We concluded that snorers exhibit a lowered hyoid position from childhood and that longitudinal changes must be explored further with a larger sample.