Automated diagnosis of schizophrenia based on spatial-temporal residual graph convolutional network.

BACKGROUND: Schizophrenia (SZ), a psychiatric disorder for which there is no precise diagnosis, has had a serious impact on the quality of human life and social activities for many years. Therefore, an advanced approach for accurate treatment is required. NEW METHOD: In this study, we provide a classification approach for SZ patients based on a spatial-temporal residual graph convolutional neural network (STRGCN). The model primarily collects spatial frequency features and temporal frequency features by spatial graph convolution and single-channel temporal convolution, respectively, and blends them both for the classification learning, in contrast to traditional approaches that only evaluate temporal frequency information in EEG and disregard spatial frequency features across brain regions. RESULTS: We conducted extensive experiments on the publicly available dataset Zenodo and our own collected dataset. The classification accuracy of the two datasets on our proposed method reached 96.32% and 85.44%, respectively. In the experiment, the dataset using delta has the best classification performance in the sub-bands. COMPARISON WITH EXISTING METHODS: Other methods mainly rely on deep learning models dominated by convolutional neural networks and long and short time memory networks, lacking exploration of the functional connections between channels. In contrast, the present method can treat the EEG signal as a graph and integrate and analyze the temporal frequency and spatial frequency features in the EEG signal. CONCLUSION: We provide an approach to not only performs better than other classic machine learning and deep learning algorithms on the dataset we used in diagnosing schizophrenia, but also understand the effects of schizophrenia on brain network features.

Clinical significance of B7-H3 expression in circulating CD4+CD25high T cells, CD14+ monocytes, and plasma for the progression of HIV infection.

BACKGROUND: B7-H3 is an important immune checkpoint molecule that plays a negative role in immune regulation. This study was aimed to explore B7-H3 expression in HIV-infected patients and its clinical significance. METHODS: To explore the expression and clinical significance of B7-H3 in HIV-infected patients, we investigated the B7-H3 expression pattern and the correlation of B7-H3 expression with clinical parameters of HIV-infected patients with different levels of CD4+ T cells. To assess the role of B7-H3 in regulating the function of T cells in HIV infection, we performed a proliferation assay and T cell function test in vitro. RESULTS: B7-H3 expression in HIV-infected patients was significantly higher than that in healthy controls. mB7-H3 expression on CD4+CD25high T cells and CD14+ monocytes increased with disease progression. mB7-H3 expression on CD4+CD25high T cells and monocytes was negatively correlated with lymphocyte count, CD4+T cell count, and positively correlated with HIV viral load in HIV-infected patients. when the number of CD4+ T cells in HIV-infected patients was ≥ 200/µL, sB7-H3 and mB7-H3 expression levels on CD4+CD25high T cells and monocytes were negatively correlated with lymphocyte count, CD4+T cell count. sB7-H3 and mB7-H3 expression on monocytes were positively correlated with HIV viral load. B7-H3 inhibited the proliferation of lymphocytes and the secretion of IFN-γ in vitro, especially the ability of CD8+ T cells to secrete IFN-γ. CONCLUSIONS: B7-H3 played an important negative regulatory role in anti-HIV infection immunity. It could be used as a potential biomarker for the progression of HIV infection and a novel target for the treatment of HIV infection.

Dieckol inhibits non-small-cell lung cancer cell proliferation and migration by regulating the PI3K/AKT signaling pathway.

Non-small-cell lung cancer (NSCLC) is one of the most prevalent type of lung cancers with an increased mortality rate in both developed and developing countries worldwide. Dieckol is one such polyphenolic drug extracted from brown algae which has proven antioxidant and anti-inflammatory properties. In the present study, we evaluated the anticancer property of dieckol against NSCLC cell line A549. The LC50 value of dieckol was found to be 25 µg/mL by performing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the antiapoptotic property of dieckol was analyzed by dual staining technique with acridine orange/propidium iodide (AO/PI) stains. It was further confirmed with flow cytometry analysis with Annexin FITC and JC-1 staining and the anti-invasive property was assessed by Transwell assay. The molecular mechanism of dieckol anticancer activity was confirmed by estimating the levels of caspases and by estimating the signaling proteins of Pi3K/AKT/mTOR signaling pathway using the immunoblotting technique. Our data suggest that dieckol is potent anticancer agent, it effectively inhibits the invasive and migratory property A549 cells and it also induces apoptosis via inhibiting Pi3K/AKT/mTOR signaling, activating the tumor suppressor protein E-cadherin signifying that dieckol is potent natural anticancer drug to treat NSCLC.

Selective Reduction of Nitro Group in Aryl Halides Catalyzed by Silver Nanoparticles Modified with ß-CD.

In this paper, we first report the selective reduction of nitro group in aryl halides catalyzed by silver nanoparticles modified with ß-CD. Taking advantage of hydrophobic lumen and donor-acceptor behavior of ß-CD, the halogenated alkyl groups on the aromatic ring can be enveloped in the inner cavity that thereby inhibits the reduction of the halogen. For validating the mechanism proposed by us, different silver nanoparticles were applied in parallel experiments. In our experiments, UV-vis spectra and NMR spectra were used to characterize the selectivity. This strategy represents an outstanding improvement on the synthesis of halogenated aromatic amines in comparison with the traditional route, and greatly expands the application of silver nanoparticles in catalytic field.

The role of LGR5 and ALDH1A1 in non-small cell lung cancer: Cancer progression and prognosis.

The Leucine rich repeat containing G protein coupled receptor 5 (LGR5), may be a candidate marker of non-small cell lung cancer (NSCLC) cells with stem cell-like properties. Aldehyde dehydrogenase 1A1 (ALDH1A1) is one of NSCLC stem cell markers. To identify the relationship of LGR5 and ALDH1A1 in NSCLC, we analyzed the expression of LGR5 and ALDH1A1 in NSCLC samples, and determined their clinical significance. We performed quantitative RT-PCR for LGR5 and ALDH1A1 expression in 24 NSCLC patients, and showed that LGR5 and ALDH1A1 mRNA were frequently increased in NSCLC tissues in comparison to that in adjacent normal tissues (p = 0.0005 and p < 0.0001, respectively). Besides, the expression of LGR5 and ALDH1A1 mRNA has a significant correlation (r = 0.416, P = 0.0483). The expression of LGR5 and ALDH1A1 in 109 NSCLC tumors and 50 adjacent normal tissues were detected by immunohistochemistry. Positive LGR5 and ALDH1A1 expression was defined in 28.4% and 41.3% of the NSCLC tumors, respectively. Further analysis indicated that 24 of these LGR5⁺ (24/31) samples expressed ALDH1A1(r = 0.3883, p < 0.0001), we also found co-localization of LGR5 and ALDH1A1 in tumor tissue samples. LGR5 and ALDH1A1 expression was significantly associated with higher pathological TNM stage of the disease (stage I + II and III + IV) (P = 0.0311 and p = 0.0221, respectively), the co-expression of LGR5 and ALDH1A1 was associated with nodal status (p = 0.0424). High expression of LGR5 or ALDH1A1 was related to poor prognosis (P = 0.0125 and p = 0.0410, respectively), and NSCLC patients with co-expression of LGR5 and ALDH1A1 had a poorer prognosis than the others (P = 0.0011). Both of them can be an independent risk factor of a poorer prognosis (P = 0.016 and P = 0.024, respectively). The expression of LGR5 and ALDH1A1 were closely associated with the tumorigenicity, metastasis and poor prognosis of NSCLC, and LGR5⁺ cells in NSCLC were likely to be the cancer cells with stem cell-like properties due to the significant correlation between LGR5 and ALDH1A1.

Changes and predictors of mental health of Chinese university students after the COVID-19 pandemic: A two-year study.

BACKGROUND: Psychological repurcussions of COVID-19 pandemic has received wide attention, but there's limited attention paid to psychological recovery afterwards. This study focuses on the changes and predictive factors of mental health of Chinese university students post-pandemic. METHODS: This study included 1175 Chinese undergraduate students sampled in May 2022 and May-June 2023, right before and after peaks of infections following the end of lockdown policy in China. The participants completed a survey of demographic variables, and three questionnaires: 12-item General Health Questionnaire, Positive Psychological Capital Questionnaire, and Prosocial Tendencies Measure. RESULTS: The participants sampled in 2023 have significant lower GHQ scores and higher PPQ scores than those sampled in 2022, while there is no significant difference in PTM scores between them. The proportion of participants with GHQ-12 scores exceeding 12 in 2023 showed slightly decrease compared to that in 2022. The infection of significant others, the sense of hope, and PPQ self-efficiency, hope and optimism subscale scores were significantly associated with GHQ-12 scores in 2023, but actual infection or quarantine experience were not. CONCLUSIONS: The mental health and psychological capital of the university students have been significantly improved within a year. It is worthy to pay attention to the infection of significant others, the sense of hope, and psychological capital in a pandemic to improve the mental health of university students. LIMITATIONS: Compared to a cross-sectional study, longitudinal research is the better choice for a two-year comparison.

Brain network analysis of working memory in schizophrenia based on multi graph attention network.

The cognitive impairment in schizophrenia (SZ) is characterized by significant deficits in working memory task. In order to explore the brain changes of SZ during a working memory task, we performed time-domain and time-frequency analysis of event related potentials (ERP) of SZ during a 0-back task. The P3 wave amplitude was found to be significantly lower in SZ patients than in healthy controls (HC) (p < 0.05). The power in the θ and α bands was significantly enhanced in the SZ group 200 ms after stimulation, while the θ band was significantly enhanced and the ß band was weakened in the HC group. Furthermore, phase lag index (PLI) based brain functional connectivity maps showed differences in the connections between parietal and frontotemporal lobes between SZ and HC (p < 0.05). Due to the natural similarity between brain networks and graph data, and the fact that graph attention network can aggregate the features of adjacent nodes, it has more advantages in learning the features of brain regions. We propose a multi graph attention network model combined with adaptive initial residual (AIR) for SZ classification, which achieves an accuracy of 90.90 % and 78.57 % on an open dataset (Zenodo) and our 0-back dataset, respectively. Overall, the proposed methodology offers promising potential for understanding the brain functional connections of schizophrenia.

Ratiometric SERS quantification of SO2 vapor based on Au@Ag-Au with Raman reporter as internal standard.

Practical gas sensing application requires sensors to quantify target analytes with high sensitivity and reproducibility. However, conventional surface enhanced Raman scattering (SERS) sensor lacks reproducibility and quantification arising from variations of "hot spot" distribution and measurement conditions. Here, a ratio-dependent SERS sensor was developed for quantitative label-free gas sensing. Au@Ag-Au nanoparticles (NPs) were filtered onto anodic aluminum oxide (AAO) forming Au@Ag-Au@AAO SERS substrate. 4-MBA was encapsulated in the gap of Au@Ag-Au and served as the internal standard (IS) to calibrate SERS signal fluctuation for improved quantification ability. Combined with headspace sampling method, SO2 residue in traditional Chinese medicine (TCM) can be extracted and captured on the immediate vicinity of Au@Ag-Au surface. The intensity ratio I613 cm-1/I1078 cm-1 showed excellent linearity within the range of 0.5 mg/kg-500 mg/kg, demonstrating superior quantification performance for SO2 detection. Signals for concentration as low as 0.05 mg/kg of SO2 could be effectively collected, much lower than the strictest limit 10 mg/kg in Chinese Pharmacopoeia. Combined with a handheld Raman spectrometer, handy and quantitative TCM quality evaluation in aspect of SO2 residue was realized. This ratiometric SERS sensor functioned well in rapid on-site SO2 quantification, exhibiting excellent sensitivity and simple operability.

[Relationship between the Expression of miRNA181a-5p and the Imbalance of Treg/Th17 in Primary Immune Thrombocytopenia].

OBJECTIVE: To investigate the role of relationship between the expression of miRNA181a-5p and imbalance of Treg/Th17 in the pathogenesis of primary immune thrombocytopenia(ITP), which contributes to clarify the mechanism of T cell immune imbalance in ITP patients. METHODS: Peripheral blood was collected from 37 ITP patients, concluding 21 untreated patients and 16 effectively treated patients, and 19 healthy controls; Peripheral blood mononuclear cells (PBMC) were isolated and the expression of miRNA181a-5p and Notch1 was analyzed by RT-PCR. The proportion of Th17 subsets and Treg cells in the peripheral circulation was detected by flow cytometer (FCM). Clinical data of ITP group was collected, including age, platelet count and disease course. RESULTS: The expression of miR-181a-5p was significantly decreased in ITP group than that of healthy control group (P＜0.01). After effective treatment, the expression of miR-181a-5p was significantly higher than that of ITP group (P＜0.05), but still significantly lower than that of healthy control group (P＜0.01); The expression of Notch1 was significantly increased in ITP group and effectively treated group than that of healthy control group (P＜0.01). There was no significant difference in proportion of Treg cells in ITP group, effectively treated group and healthy control group (P＞0.05). The proportion of Th17 subsets in ITP group was significantly increased than that of healthy control group (P＜0.05), while the ratio of Treg/Th17 was significantly decreased (P＜0.05). There was a positive correlation between the expression of miR-181a-5p and ratio of Treg/Th17 in ITP group (r=0.555). CONCLUSION: The expression of miR-181a-5p is significantly decreased in ITP patients, which is closely related to the imbalance of Treg/Th17 cells. After effective treatment, the expression of miR-181a-5p can be significantly corrected, but still failed to reach the level of healthy people. While the expression of Notch1 is significantly increased in ITP patients, and could not reach the level of healthy people after effective treatment.

Abnormality of Functional Connections in the Resting State Brains of Schizophrenics.

To explore the change of brain connectivity in schizophrenics (SCZ), the resting-state EEG source functional connections of SCZ and healthy control (HC) were investigated in this paper. Different band single-layer networks, multilayer networks, and improved multilayer networks were constructed and their topological attributes were extracted. The topological attributes of SCZ and HC were automatically distinguished using ensemble learning methods called Ensemble Learning based on Trees and Soft voting method, and the effectiveness of different network construction methods was compared based on the classification accuracy. The results showed that the classification accuracy was 89.38% for α band network, 82.5% for multilayer network, and 86.88% for improved multilayer network. Comparing patients with SCZ to those with Alzheimer's disease (AD), the classification accuracy of improved multilayer network was the highest, which was 88.12%. The power spectrum in the α band of SCZ was significantly lower than HC, whereas there was no significant difference between SCZ and AD. This indicated that the improved multilayer network can effectively distinguish SCZ and other groups not only when their power spectrum was significantly different. The results also suggested that the improved multilayer topological attributes were regarded as biological markers in the clinical diagnosis of patients with schizophrenia and even other mental disorders.

Enhanced Catalytic Activity of Magnetic Bimetallic Ag-Au Nanoparticles Mediated by Surface Plasmon Resonance.

We firstly discover the enhanced catalytic activity of magnetic noble metal nanoparticles mediated by surface plasmon resonance. Under light irradiation with certain wavelength, the catalytic performance of magnetic noble metal nanoparticles shows changes with different degrees and directions that are associated with the surface plasmon resonance (SPR) of the noble metal. Moreover, the coupling of silver and gold allows the catalytic performance of magnetic bimetallic Ag-Au nanoparticles to show more positive response to surface plasmon resonance. The magnetic bimetallic Ag-Au nanoparticles show excellent catalytic performance toward the reduction reaction of aromatic nitro group, and corresponding rate constant of the catalytic reduction reaction increases about three times with light irradiation.

Kininogen-Nitric Oxide Signaling at Nearby Nonexcited Acupoints after Long-Term Stimulation.

Acupuncture treatment is based on acupoint stimulation; however, the biological basis is not understood. We stimulated one acupoint with catgut embedding for 8 weeks and then used isobaric tags for relative and absolute quantitation to screen proteins with altered expression in adjacent acupoints of Sprague Dawley rats. We found that kininogen expression was significantly upregulated in the stimulated and the nonstimulated adjacent acupoints along the same meridian. The enhanced kininogen expression was meridian dependent and was most apparent among small vessels in the subcutaneous layer. Enhanced signals of nitric oxide synthases, cGMP-dependent protein kinase, and myosin light chain were also observed at the nonstimulated adjacent acupoints along the same meridian. These findings uncover biological changes at acupoints and suggest the critical role of the kininogen-nitric oxide signaling pathway in acupoint activation.

Transient alterations in slow oscillations of hippocampal networks by low-frequency stimulations on multi-electrode arrays.

Slow oscillations in the hippocampus are correlated with memory consolidation and brain diseases. The characteristic firings of the hippocampal network in vitro are still poorly understood. Here, spontaneous oscillations(~0.004 Hz) were found in high-density hippocampal networks by multi-electrode arrays after 30 days in vitro.This kind of spontaneous activity was characterized by periodic synchronized superbursts, which persisted for approximately 60 s at long intervals. Additionally, 1-Hz stimulation (duration <120 s) could regulate these network wide oscillatory activities by triggering the next synchronized superbursts prematurely. The results demonstrated that the slow oscillatory activities in hippocampal cultures could be regulated by external stimulation, which indicates that multi-electrode arrays provide a well-suited platform for studying the dynamics of slow oscillations in vitro and may help to elucidate the mechanism of electrical stimulation therapy.

pH-Mediated Synthesis and Mechanistic Study of Homogeneous Magnetic Ag@Fe3O4 Nanoparticles.

In this paper, we report a novel kind of pH-mediated homogeneous magnetic Ag@Fe3O4 nanoparticles prepared by facile one-pot synthesis. The nanostructure and surface element composition along with magnetism of the as-synthesized hybrid nanoparticles can be easily adjusted by pH value in synthetic process. Furthermore, XRD and XPS detections indicated that the two components in the nanoparticles are both independent and certain synergistic. Compared with magnetic silver nanoparticles prepared by traditional multi-step methods, the homogeneous Ag@Fe3O4 nanoparticles showed excellent monodispersity and stability. Moreover, corresponding formation mechanism of the homogeneous hybrid magnetic nanoparticles was demonstrated in detail. Catalytic application of the homogeneous hybrid nanoparticles prepared under different pH values also verified rationality of the formation mechanism from side. This research provides a general strategy for constructing and large-scale preparing homogeneous magnetic hybrid metal nanoparticles.

Phylogeography of Dendrolimus punctatus (Lepidoptera: Lasiocampidae): Population differentiation and last glacial maximum survival.

Although the Masson pine moth, Dendrolimus punctatus, is one of the most destructive forest pest insects and is an endemic condition in China, we still do not fully understand the patterns of how its distribution range varies in response to Quaternary climatic oscillations. Here, we sequenced one maternally inherited mitochondrial gene (COI) and biparentally inherited nuclear data (ITS1 and ITS2) among 23 natural populations across the entire range of the species in China. A total of 51 mitotypes and 38 ribotypes were separately obtained using mtDNA and ITS1 data. Furthermore, significant phylogeographical structure (N ST > G ST, p < 0.01) were detected. The spatial distribution of mitotypes implied that two distinct groups existed in the species: one in the southwest distribution, including 10 locations, and the other located in the northeast region of China. It is suggested, therefore, that each group was derived from ancestors that occupied different isolated refugia during previous periods, possibly last glacial maximum. Mismatch distribution and Bayesian population dynamics analysis suggested the population size underwent sudden expansion, which is consistent with the results of ecological niche modeling. As a typical phytophagous insect, the history of population expansion was in accordance with the host plants, providing abundant food resources and habitat. Intraspecific success rate of barcoding identification was lower than interspecific ones, indicating a level of difficulty in barcoding individuals from different populations. However, it still provides an early insight into the pattern of genetic diversity within a species. OPEN RESEARCH BADGES: This article has been awarded an Open Data and Open Materials. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.2df87g2. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Lysine acetylproteome profiling under water deficit reveals key acetylated proteins involved in wheat grain development and starch biosynthesis.

Lysine acetylation is a widespread protein posttranslational modification in all organisms. However, quantitative acetylproteome characterization in response to water deficit during crop grain development remains unknown. In the study, we performed the first large-scale acetylproteome analysis of developing wheat grains under water-deficit using label-free quantitative proteome approach. In total, 716 acetylated sites corresponding to 442 acetylated proteins were identified, of which 106 acetylated sites representing 93 acetylated proteins (including 88 non-histones) showed significant changes under water-deficit. The functional classification showed that 57% and 20% of acetylated proteins were related to metabolic and cellular processes, respectively. Water-deficit caused widespread functional crosstalk between protein acetylation and other PTMs. Particularly, both acetylation and phosphorylation occurred in two key enzymes involved in starch biosynthesis, sucrose synthase (SuSy) and ADP glucose pyrophosphorylase (AGPase). Their crosstalk could play important roles in starch biosynthesis and yield formation under drought conditions. Western blot analysis combined with tandem mass spectrometry identification further verified the reliability of the acetylproteome results. Most of the acetylated proteins showed consistences between transcription and post-translation levels by quantitative real-time PCR. A putative metabolic pathway was proposed to dissect the roles of protein acetylation in regulation of drought response and defense during wheat grain development. SIGNIFICANCE: Lysine acetylation is a widespread modification in all organisms. We performed the first large-scale acetylproteome analysis of developing wheat grains under water-deficit and revealed key acetylated proteins involved in wheat grain development and starch biosynthesis.

Osteocalcin Ameliorates Motor Dysfunction in a 6-Hydroxydopamine-Induced Parkinson's Disease Rat Model Through AKT/GSK3ß Signaling.

Osteoblasts derived osteocalcin (OCN) is recently reported to be involved in dopaminergic neuronal development. As dopaminergic neuronal injury in the substantia nigra (SN) is a pathological hallmark of Parkinson's disease (PD), we investigated whether OCN could exert protective effects on 6-hydroxydopamine (6-OHDA)-induced PD rat model. Our data showed that the OCN level in the cerebrospinal fluid (CSF) in PD rat models was significantly lower than that in controls. Intervention with OCN could improve the behavioral dysfunction in PD rat models and reduce the tyrosine hydroxylase (TH) loss in the nigrostriatal system. In addition, OCN could inhibit the astrocyte and microglia proliferation in the SN of PD rats. In vitro studies showed that OCN significantly ameliorated the neurotoxicity of 6-OHDA through the AKT/GSK3ß signaling pathway. In summary, OCN plays a protective role against parkinsonian neurodegeneration in the PD rat model, suggesting a potential therapeutic use of OCN in PD.

Nicotinamide adenine dinucleotide suppresses epileptogenesis at an early stage.

The pathophysiologic mechanisms of epileptogenesis are poorly understood, and no effective therapy exists for suppressing epileptogenesis. Numerous reports have shown that nicotinamide adenine dinucleotide (NAD+) has neuroprotective effects, suggesting its potential use for treating epileptogenesis. Here we evaluated the effects of NAD+ on epileptogenesis and the mechanisms underlying these effects. In pilocarpine-induced status epilepticus (SE) model mice, NAD+ was injected three times within 24.5 h after SE. NAD+ intervention significantly reduced the incidence of spontaneous recurrent seizure (SRS) and abnormal electroencephalogram (EEG) activity, rescued contextual fear memory formation, reduced neuronal loss in the CA1 region of the hippocampus at SRS stage. Furthermore, exogenous supply of NAD+ distinctly reversed the seizure-induced depletion of endogenous NAD+, reduced neuronal apoptosis in the CA1 region of the hippocampus, and reversed the augmented Acp53/p53 ratio at the early stage of epileptogenesis. Our findings demonstrated that early-stage intervention with NAD+ prevents epileptogenesis in pilocarpine-induced SE mice by suppressing neuronal apoptosis.

Extrasynaptic NMDA receptor dependent long-term potentiation of hippocampal CA1 pyramidal neurons.

In the adult mouse hippocampus, NMDA receptors (NMDARs) of CA1 neurons play an important role in the synaptic plasticity. The location of NMDARs can determine their roles in the induction of long-term potentiation (LTP). However, the extrasynaptic NMDARs (ES-NMDARs) dependent LTP haven't been reported. Here, through the use of a 5-Hz stimulation and MK-801 (an irreversible antagonist of NMDARs) in the CA1 neurons of adult mice hippocampal slices, synaptic NMDARs were selectively inhibited and NMDAR-mediated excitatory postsynaptic currents were not recovered. We found that a robust LTP was induced by 3-train 100-Hz stimulation when the synaptic NMDARs and extrasynaptic NR2B containing NMDARs were blocked, but not in the any of the following conditions: blocking of all NMDARs (synaptic and extrasynaptic), blocking of the synaptic NMDARs, and blocking of the synaptic NMDARs and extrasynaptic NR2A-containing NMDARs. The results indicate that this LTP is ES-NMDARs dependent, and NR2B-containing ES-NMDARs modulates the threshold of LTP induction.

Mechanisms by which tumor cells and monocytes expressing the angiogenic factor thymidine phosphorylase mediate human endothelial cell migration.

The angiogenic factor thymidine phosphorylase (TP) is highly expressed in many human solid tumors, and the level of its expression is associated with tumor neovascularization, invasiveness, and metastasis and with shorter patient survival time. TP promotes endothelial cell (EC) migration in vitro and angiogenesis in vivo, and these have been linked to its enzymatic activity. The mechanism by which TP stimulates EC migration was investigated using human umbilical vein ECs (HUVECs). TP induced concentration-dependent HUVEC migration, which required a TP gradient and thymidine and which was abrogated by the TP inhibitor CIMU (5-chloro-6(1-imidazolylmethyl)uracil). The chemotactic actions of TP plus thymidine were duplicated by the TP metabolite, 2-deoxyribose-1-phosphate (dR-1-P), and 10-fold more potently by its subsequent metabolite, 2-deoxyribose (2dR). Migration induced by dR-1-P, but not 2dR, was blocked by an alkaline phosphatase inhibitor, suggesting that the actions of dR-1-P first required its conversion to 2dR. In the migration assay, [5'-3H]dThd was metabolized to dR-1-P (96%) and 2dR (3.8%), and a gradient of both metabolites was maintained between the lower and upper chambers over the entire 5-h assay. TP expression in human solid tumors occurs in both tumor epithelial cells and in tumor-associated macrophages. The migration assay was adapted to use TP-transfected carcinoma cells to stimulate HUVEC migration, and they were found to induce more migration than did control vector-transfected cells. Human monocyte cells U937 and THP1, which constitutively expressed high levels of TP, also strongly induced HUVEC migration in the coculture assay. CIMU inhibited tumor-cell and monocyte-induced migration. In contrast, a neutralizing antibody to TP had no effect on cell-stimulated HUVEC migration, even though it completely blocked the migration mediated by purified TP. Thus, the intracellular actions of TP were sufficient to stimulate HUVEC chemotaxis. In contrast to purified TP, when incubated with [5'-3H]-thymidine, cells expressing TP released up to 20-fold more 2dR into the medium than dR-1-P. These studies demonstrate that TP-expressing cells mediate EC migration via the intracellular metabolism of thymidine and subsequent extracellular release of 2dR, which forms a chemotactic gradient.