[Research status and prospect of immunotherapy in gastrointestinal stromal tumors].

Tyrosine kinase inhibitors (TKI) significantly reduce the risk of recurrence and metastasis and prolong survival in patients with gastrointestinal stromal tumors (GIST), but drug resistance is often inevitable. Immunotherapy has been proven effective in multiple solid tumors, but the efficacy in GIST is unclear. The efficacy of immunotherapy depends on the tumor microenvironment (TME). Tumor-infiltrating immune cells and immune checkpoints are important components of TME, which not only participate in the regulation of tumor immune response but are also the key target of immunotherapy. A comprehensive analysis of them can clarify the mechanism of tumor immune escape. This review found that there are abundant tumor-infiltrating immune cells in GIST, which play an important role in tumor immune surveillance and escape. Although early clinical studies have shown that patients with GIST have a good tolerance to immunotherapy, the curative effect is not satisfactory. Therefore, how to select the responders of immunotherapy and coordinate the relationship between immunotherapy and TKIs is the key issue to be explored. At the same time, the gradual deepening of basic research and large sample prospective clinical trials will certainly provide more strategies for the application of immunotherapy in GIST.

[Evaluation of diagnostic efficacy of digital liquid chip method for detection of specific antineutrophil cytoplasmic antibodies].

To explore the clinical diagnostic efficacy of antineutrophil cytoplasmic antibody associated vasculitis (AAV) by comparing the consistency and coincidence rate of serum anti-myeloperoxidase (MPO) antibody and anti-protease 3 (PR3) antibody detected by digital liquid chip method (DLCM) and enzyme-linked immunosorbent assay (ELISA). To provide reference for the selection of detection methods of anti-MPO antibody and anti-PR3 antibody in clinical laboratory. This study is a cross-sectional study, a total of 307 cases of antineutrophil cytoplasmic antibodies were detected in the Department of Clinical Immunology, West China Hospital of Sichuan University from January to March 2021. The serum samples and related clinical information were collected. At the same time, the levels of anti-MPO antibody and anti-PR3 antibody in serum samples were detected by ELISA and DLCM, indirect immunofluorescence (IIF) was used to re-test the differential samples between the two methods. SPSS 26.0 was used to analyze the test results, Cohen's kappa coefficient analysis was used to compare the consistency of the two methods, and paired chi-square test was used to compare the sensitivity and specificity of the two methods to AAV. The results showed that the positive cases of anti-MPO antibody detected by ELISA and DLCM were 63 and 44, and the negative cases were 244 and 263; the positive cases of anti-PR3 antibody detected by ELISA and DLCM were 34 and 28, and the negative cases were 273 and 279. The results of anti-MPO antibody and anti-PR3 antibody detected by the two methods had good consistency and coincidence rate, in which the total coincidence rate of anti-MPO antibody was 92.51%, the positive coincidence rate was 66.67%, and the negative coincidence rate was 99.18%. The results of consistency analysis showed that kappa=0.741 had well consistency. The total coincidence rate of anti-PR3 antibody is 96.74%, the positive coincidence rate is 76.47%, and the negative coincidence rate is 99.27%. The consistency analysis results show that kappa=0.821 had strong consistency. The results of IIF re-test of differential samples showed that the coincidence rate between DLCM and IIF was higher. The results of comparative analysis of anti-MPO antibody and anti-PR3 antibody showed that the specificity of DLCM was better than that of ELISA, and its sensitivity was lower than that of ELISA. In conclusion, the results of anti-MPO antibody and anti-PR3 antibody detected by DLCM were consistent with those of ELISA. In the combined detection of anti-MPO antibody and anti-PR3 antibody, the specificity of DLCM is better than that of ELISA.

[Interpretation for the group standards in technical specification for health risk investigation of central air conditioning ventilation system during coronavirus disease 2019 epidemic].

The central air conditioning ventilation system plays an important role in the air circulation of buildings such as centralized isolation medical observation points and general public buildings. In order to meet the requirements of COVID-19 epidemic prevention and control, Beijing Preventive Medicine Association organized Beijing CDC and other professional institutes to write up the group standard entitled "Technical specification for health risk investigation of central air conditioning ventilation system during the COVID-19 epidemic (T/BPMA 0006-2020)" . According to the particularity of central air conditioning ventilation system risk control during the outbreak of similar respiratory infectious diseases, based on current laws and regulations and the principle of scientific, practical, consistency and normative, 8 key points of risk investigations were summarized, which were the location of fresh air outlet, air conditioning mode, air return mode, air system, air distribution, fresh air volume, exhaust and air conditioner components. The contents, process, method, data analysis and conclusion of the investigation implementation were also defined and unified. It could standardize and guide institutions such as disease control and health supervision to carry out relevant risk managements, and provided solutions and technical supports for such major public health emergencies in city operations.

[Clinicopathological features and prognosis of 59 patients with platelet-derived growth factor α-mutant gastrointestinal stromal tumor].

Objective: Platelet-derived growth factor α (PDGFRA)-mutant gastrointestinal stromal tumor (GIST) is a relatively rare disease, whose clinicopathological characteristics and prognosis have been poorly studied. In this paper, the clinicopathological features and prognostic factors of PDGFRA-mutant GIST are investigated to provide more data for its understanding and treatment. Methods: A retrospective case-control study was used to collect the medical records of patients with GIST who underwent surgical resection in Zhongshan Hospital of Fudan University from January 2015 to August 2019. Patients with PDGFRA-mutant GIST were enrolled, and those with synonymous PDGFRA mutations, non-tumor-related deaths, and lack of clinicopathological data were excluded. The clinicopathological data were collected and the risk factors associated with prognosis were analyzed. Results: Among the enrolled 59 patients, there were 41 males (69.5%) and 18 females (30.5%) with the median age of 60 (25-79) years. All tumors originated from the stomach. The tumor size was 5 (3-7) cm, and the mitotic count was 2 (1-4)/50 high-power fields (HPF). According to the modified NIH risk stratification, 8 cases were classified as very low risk (13.6%), 25 cases as low risk (42.4%), 14 cases as moderate risk (23.7%), and 12 cases as high risk (20.3%). There were 7 cases of exon 12 mutation and 52 cases of exon 18 mutation (including 36 cases of D842V mutation). A comparison of clinicopathological features between the D842V mutation group and the non-D842V mutation group showed no statistically significant difference (all P>0.05). During a median follow-up of 21 (0-59) months, the 1- and 3-year relapse-free survival (RFS) rates of all the patients were 96.6% and 91.5%, respectively. There were 8 cases of recurrence and 3 cases of death. Six GIST patients with D842V mutation had tumor recurrence after operation, of whom 4 cases achieved varying degrees of tumor remission after being treated with dasatinib or avapritinib. Log-rank analysis showed that the overall survival (OS) of male was better than that of female (100% vs. 83.3%, P=0.046), but there was no significant difference in OS among patients with different risk grades (P=0.057). The RFS and OS of patients with D842V mutation and non-D842V mutation, exon 12 and exon 18 mutation were similar (all P>0.05). Univariate Cox analysis showed that RFS was associated with gender (P=0.010), tumor size (P=0.042), mitotic count (P=0.003), and the modified NIH risk stratification (P=0.042), while multivariate analysis revealed that higher risk grade was an independent risk factor for recurrence of PDGFRA-mutant GIST (HR=12.796, 95%CI: 1.326-123.501, P=0.028). Gender was an independent factor for recurrence, and the risk of recurrence in males was lower than that in females (HR=0.154, 95%CI: 0.028-0.841, P=0.031). Conclusions: Gender and the modified NIH risk stratification are independent risk factors for recurrence of PDGFRA-mutant GIST, while patients with D842V and non-D842V mutation, and exon 12 and exon 18 mutation have a similar risk of recurrence and death.

[Research advance of liquid biopsy in gastrointestinal stromal tumors].

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumors in the gastrointestinal tract. Surgical resection is the only curative treatment, while imatinib is the first-line therapy for recurrent, metastatic, and unresectable GIST. However, more than half of GIST patients suffer from secondary resistance to imatinib within 2 years after treatment initiation. Therefore, early diagnosis, drug resistance and recurrence surveillance are critical for GIST patients. Liquid biopsy is a new method which utilizes the detection of tumor biomarkers in peripheral blood for early diagnosis and therapeutic efficacy assessment. In recent years, liquid biopsy has achieved significant research progress in several kinds of malignancy. This review aims at presenting an overview on research advance of liquid biopsy in GIST and may provide a new method for early diagnosis and therapeutic efficacy assessment of GIST.

Clinical outcomes of different therapeutic modalities for rectal gastrointestinal stromal tumor: Summary of 14-year clinical experience in a single center.

OBJECTIVE: The optimal treatment for gastrointestinal stromal tumor (GIST) of the rectum is controversial due to the extremely low incidence of the disease. The aim of the present study was to compare the clinical outcomes of different treatment modalities for rectal GIST by reviewing the 14-year experience in our center. METHOD: Medical records of rectal GIST patients who received surgical treatment in our center between January 2004 to December 2017 were reviewed retrospectively. Overall survival (OS) and recurrence-free survival (RFS) were used as the observation endpoints. RESULTS: Included in this study were 71 GIST patients, including 42 patients who underwent local excision (LE) and 29 patients who underwent segmental resection (SR). There were differences in tumor size (P = 0.001) and malignant risk grade (P = 0.007). The LE approach achieved a lower rate of R0 resection than SR (29/42 vs.27/29, P = 0.015) and shorter hospital stay (P = 0.004). Preoperative imatinib mesylate (IM) therapy improved the rate of sphincter-sparing surgery for patients with tumors in the very low segment of the rectum (P = 0.012) and offered better R0 resection margins (P = 0.027). Multivariate analysis showed that the resection margin status (P = 0.014), risk stratification (P = 0.001) and IM therapy (P = 0.042) were independent factors affecting RFS of rectal GIST patients but not the surgical modalities (LE vs. SR, P = 0.802). Multivariate analysis showed no significant impact of these variables on OS. CONCLUSION: Selection of surgical modalities has no significant impact on the prognosis. Local excision is the preferred surgical modality for resectable rectal GIST by virtue of less injury and shorter hospital stay. IM therapy has proved to be associated with improved RFS for rectal GIST patients.

[Research advances in the secondary resistance mechanism of imatinib in gastrointestinal stromal tumors].

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumors in the gastrointestinal tract. Though surgical resection is the only radical treatment, postoperative recurrence and metastasis often occur. The first-line therapy for the treatment of recurrent, metastatic and unresectable GIST is imatinib. More than 80% of patients can benefit from imatinib treatment, but half of patients will still have recurrence or metastasis within 2 years after treatment initiation, and secondary drug resistance is a major cause of disease progression. Therefore, adeep understanding of the mechanisms of secondary drug resistance will guide us to develop personalized therapeutic schedule in the future. This article describes the mechanism of IM secondary resistance from the aspects of gene alteration, abnormal activation of signal transduction pathway, autophagy, apoptosis and drug concentration. It is found that single drug therapy has certain limitations in patients with secondary resistance to IM. Using IM combined with downstream signaling molecule inhibitors, autophagy inhibitors, insulin-like growth factor 1 receptor (IGF-1R) inhibitors, heat shock protein 90 (HSP90) inhibitors, cytotoxic T lymphocyte - associated antigen - 4 (CTLA - 4) antibodies and mitochondrial inhibitors provide us new therapeutic ideas. However, these combination treatments are still in the research phase, and further trials are needed to confirm the safety and efficacy. With the gradual deepening of research on drug resistance mechanisms, it will provide more solutions to the current serious drug resistance problem.

Exploratory social network analysis and gene sequencing in people who inject drugs infected with hepatitis C virus.

Social networks facilitate the transmission of hepatitis C virus (HCV) in people who inject drugs (PWID). The aim of this study was to assess how certain network structural characteristics are related to HCV infections in PWID and to determine the most susceptible individuals for HCV transmission in a network of PWID. PWID (N = 80) from central China were recruited from a previous follow-up case-control study. Demographic and behavioural information was obtained from a computerized database for each group. HCV RNA was extracted from blood specimens. Sequences were used to construct a phylogenetic tree and to determine genetic distances. Socio-metric social links were established between participants. Network measures were calculated using UCINET. Three HCV genotypes were identified, covering five subtypes. The density of the social networks for the whole sample (N = 80), case group (n = 31) and control group (n = 49) was 0.038, 0.054 and 0.008, respectively. PWID infected with HCV were in frequent contact with others within their group. There were four pairs of nodes with genotypic distances of 0.000 that were identified and clustered in subtypes 6a and 1b; each subject pair was linked and found in one clique. Three of the five most active nodes were infected with HCV. These three nodes served as a bridge, contributing to the connection of other nodes. These findings identify susceptible individuals for HCV transmission in PWID based on their frequent contact with others in the network. These results provide data that could be used for modelling HCV transmission patterns and in public health policies.

Glucagon-like peptide-1 regulates mitochondrial biogenesis and tau phosphorylation against advanced glycation end product-induced neuronal insult: Studies in vivo and in vitro.

Our previous study has proved that glucagon-like peptide-1 (GLP-1), which is developed to treat type 2 diabetes, has a significant effect on neuroprotection against advanced glycation end product (AGE)-induced neuronal insult in vitro models of diabetes-related Alzheimer's disease (AD). However, the molecular mechanisms remain to be elucidated and it is not clear whether GLP-1 receptor mediates the down-regulation effects on AGE-induced AD-like changes in vivo. This study aims to explore the effect and mechanisms of GLP-1 receptor agonists (GLP-1RA) against the AGE-dependent signaling pathway both in vitro and in vivo. In this study, we demonstrated that GLP-1RA could inhibit oxidative stress and repair mitochondrial damage in addition to decreasing tau hyperphosphorylation in PC12 cells treated with AGEs. Importantly, we first observed AGEs in the circulatory system could induce tau hyperphosphorylation after we injected AGEs (1µg/kg bodyweight) into the mice tail vein. We found GLP-1RA could promote mitochondrial biogenesis and antioxidant system via regulating peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) signaling pathway in vivo besides down-regulating the activity of glycogen synthase kinase 3ß (GSK-3ß) to reverse tau hyperphosphorylation directly. Collectively, our results suggest that GLP-1RA protects neurons against AGE-induced tau hyperphosphorylation via regulating GSK-3ß and PGC-1α two cooperative signaling pathways.

Predictive role of RRM1 and BRCA1 mRNA expression on the clinical outcome of advanced non-small cell lung cancer.

This study aimed to evaluate the association between RRM1 and BRCA1 expressions and the therapeutic efficacy of platinum-based chemotherapy in non-small cell lung cancer patients in terms of their response and prognosis. In total, 377 patients agreed to participate in our study, and all of them received platinum-based combination chemotherapy between January 2008 and January 2009. The relative cDNA quantitation for RRM1 and BRCA1 was conducted using a fluorescence-based, real-time detection method, using ß-actin as a reference gene. The average age of the 377 patients was 64.6 years (range: 25.5-86.4 years), including 269 men and 108 women. Patients with high RRM1 expression benefited more from a platinum-containing regimen, and patients with high BRCA1 expression showed a high response rate to a platinum-containing regimen and reduced disease progression. Patients with high RRM1 expression were associated with a longer progression-free survival (PFS) and overall survival (OS) than those with low expression, and the hazard ratios (HRs) (95% confidence interval (CI)) were 0.67 (0.32-0.91) and 0.54 (0.30-0.95), respectively. Patients with high BRCA1 expression showed longer PFS and OS compared to those with low expression, and the HRs (95%CI) were 0.54 (0.30-0.95) and 0.62 (0.32-0.93), respectively. These results could be used in personalized chemotherapy decisions and to increase the response rate and prolonged survival, and could encourage exploration of the predictive value of other genes.

Removal of waterborne pathogens from liver transplant unit water taps in prevention of healthcare-associated infections: a proposal for a cost-effective, proactive infection control strategy.

Hospital water supplies often contain waterborne pathogens, which can become a reservoir for healthcare-associated infections (HAIs). We surveyed the extent of waterborne pathogen contamination in the water supply of a Liver Transplant Unit. The efficacy of point-of-use (POU) water filters was evaluated by comparative analysis in routine clinical use. Our baseline environmental surveillance showed that Legionella spp. (28%, 38/136), Pseudomonas aeruginosa (8%, 11/136), Mycobacterium spp. (87%, 118/136) and filamentous fungi (50%, 68/136) were isolated from the tap water of the Liver Transplant Unit. 28.9% of Legionella spp.-positive water samples (n = 38) showed high-level Legionella contamination (≥10(3) CFU/L). After installation of the POU water filter, none of these pathogens were found in the POU filtered water samples. Furthermore, colonizations/infections with Gram-negative bacteria determined from patient specimens were reduced by 47% during this period, even if only 27% (3/11) of the distal sites were installed with POU water filters. In conclusion, the presence of waterborne pathogens was common in the water supply of our Liver Transplant Unit. POU water filters effectively eradicated these pathogens from the water supply. Concomitantly, healthcare-associated colonization/infections declined after the POU filters were installed, indicating their potential benefit in reducing waterborne HAIs.

Glucagon-like peptide-1 protects hippocampal neurons against advanced glycation end product-induced tau hyperphosphorylation.

We have previously demonstrated that glucagon-like peptide-1 (GLP-1) receptor agonist ameliorated neurodegenerative changes in rat models of diabetes-related Alzheimer's disease (AD), and protected neurons from glucose toxicity in vitro. Herein, we investigated the effects of GLP-1 receptor mediates on cell toxicity and tau hyperphosphorylation induced by advanced glycation end products (AGEs), which are associated with glucose toxicity, and the molecular mechanism in PC12 cells and the primary hippocampal neurons. Our study demonstrated that the similar protection effects of GLP-1 existed in PC12 cells treated with glucose-bovine serum albumin (BSA) in hyperglycemic conditions or with glycoaldehyde-BSA alone. Additionally, glucose-BSA alone did not induce significant cytotoxicity in PC12 cells, but resulted in tau hyperphosphorylation in primary hippocampal neurons in 24h. And we found that GLP-1 could reduce cell tau phosphorylation induced by high glucose or glucose-BSA. Furthermore, our data in the present study suggested that GLP-1 regulated tau phosphorylation induced by AGEs through a signaling pathway involving glycogen synthase kinase 3ß (GSK-3ß), similarly to the GSK-3ß inhibitor, lithium chloride. Our findings suggest that GLP-1 can protect neurons from diabetes-associated AGE insults in vitro, and provide new evidence for a potential therapeutic value of GLP-1 receptor agonist in the treatment of AD especially diabetes-related AD.

Polymorphisms in toll-like receptors 2, 4 and 5 are associated with Legionella pneumophila infection.

PURPOSE: To investigate whether single-nucleotide polymorphisms (SNPs) in toll-like receptors (TLR) 2, 4 and 5 affect the susceptibility of Legionella pneumophila infection in a Han Chinese population by in vitro assay. METHODS: Fifty-four (n = 54) healthy subjects were genotyped for SNPs (TLR2 (C597T) [rs3804099], TLR4 (G2244A), TLR4 (A2299G) [AF177765] and TLR5 (C1174T) [rs5744168]). Peripheral blood mononuclear cells (PBMCs) were obtained from these subjects and stimulated with live L. pneumophila for 24 h. The mRNA expression levels of adapter protein myeloid differentiation factor 88 (MyD88) were determined using real-time reverse transcription polymerase chain reaction (RT-PCR) and the expression levels of TNF-α, IL-1ß and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: After 24 h of L. pneumophila stimulation, the mRNA expression level of MyD88 was significantly lower with TLR2 (C597T) CT/TT (p = 0.0482) or TLR5 (C1174T) CC homozygotes (p = 0.0223) in comparison to PBMCs with other genotypes. The mRNA expression level of MyD88 was significantly higher with TLR4 (G2244A) GG/GA than AA homozygotes (p = 0.0352). No significant difference was found in PBMCs with genotypes TLR4 (A2299G) AA, AG or GG (p > 0.05). Supernatant from cultures of PBMCs with genotype TLR2 (C597T) CT/TT or TLR5 (C1174T) CC were found to have higher levels of TNF-α, IL-1ß and IL-6 after L. pneumophila stimulation. TLR4 (G2244A) GG/GA alleles were found to have lower levels of TNF-α (p = 0.0367) and higher levels of IL-6 (p = 0.0317) in comparison to cells with AA alleles. No significant association was observed between the TNF-α, IL-1ß and IL-6 levels and genotype TLR4 (A2299G) after L. pneumophila stimulation (p > 0.05). CONCLUSION: Our findings suggested that healthy subjects who were positive for the TLR2 (C597T) CT/TT and TLR5 (C1174T) CC alleles had a superior innate immune response to L. pneumophila than other genotypes in the evaluated Han Chinese population, whereas no association was found for the TLR4 (A2299G) [AF177765] polymorphism with L. pneumophila susceptibility. It is not clear from our study if TLR4 (G2244A) [AF177765] is associated with susceptibility to L. pneumophila infection.

Optimization of auto-induction medium for G-CSF production by Escherichia coli using artificial neural networks coupled with genetic algorithm.

Granulocyte colony-stimulating factor (G-CSF) is a cytokine widely used in cancer patients receiving high doses of chemotherapeutic drugs to prevent the chemotherapy-induced suppression of white blood cells. The production of recombinant G-CSF should be increased to meet the increasing market demand. This study aims to model and optimize the carbon source of auto-induction medium to enhance G-CSF production using artificial neural networks coupled with genetic algorithm. In this approach, artificial neural networks served as bioprocess modeling tools, and genetic algorithm (GA) was applied to optimize the established artificial neural network models. Two artificial neural network models were constructed: the back-propagation (BP) network and the radial basis function (RBF) network. The root mean square error, coefficient of determination, and standard error of prediction of the BP model were 0.0375, 0.959, and 8.49 %, respectively, whereas those of the RBF model were 0.0257, 0.980, and 5.82 %, respectively. These values indicated that the RBF model possessed higher fitness and prediction accuracy than the BP model. Under the optimized auto-induction medium, the predicted maximum G-CSF yield by the BP-GA approach was 71.66 %, whereas that by the RBF-GA approach was 75.17 %. These predicted values are in agreement with the experimental results, with 72.4 and 76.014 % for the BP-GA and RBF-GA models, respectively. These results suggest that RBF-GA is superior to BP-GA. The developed approach in this study may be helpful in modeling and optimizing other multivariable, non-linear, and time-variant bioprocesses.

Sulfation of a polysaccharide produced by a marine filamentous fungus Phoma herbarum YS4108 alters its antioxidant properties in vitro.

Free radicals and other reactive oxygen species (ROS) are generated by all aerobic cells and are widely believed to play a significant role in aging as well as a number of degenerative or pathological diseases. This study compared the free radical-scavenging properties and antioxidant activity of YCP, a polysaccharide from the mycelium of a marine filamentous fungus Phoma herbarum YS 4108 and its two chemically sulfated derivatives YCP-S1 and YCP-S2. Sulfation, which masks hydroxyl groups of YCP polysaccharide molecule, could introduce new antioxidant activity, such as superoxide and hydroxyl radicals scavenging activity, metal chelating action, lipid peroxidation and linoleic acid oxidation inhibition capability. Furthermore, sulfated YCP was more potent than YCP at protecting erythrocytes against oxidative damage hemolysis. The current data suggest for the first time that sulfation of polysaccharide significantly increases its antioxidant activity and the chemical modification of polysaccharides may allow the preparation of derivatives with new properties and a variety of applications.

Purification, characterization and enzymatic degradation of YCP, a polysaccharide from marine filamentous fungus Phoma herbarum YS4108.

YCP, a mitogenic polysaccharide with its molecular weight (MW) of 2.4 x 10(3) kDa, was isolated from the mycelium of the marine filamentous fungus Phoma herbarum YS4108 by a combination of ion-exchange chromatography on DEAE-32 and gel permeation over Sephacryl S-400. The detailed compositional, spectroscopic and methylation analyses of the polysaccharide demonstrated that its backbone possessed most likely a linear alpha-(1 --> 4) bonded glucopyranoside main chain co-bearing through side alpha-(1 --> 6)-linkage. The alpha-(1 --> 4) bondage of the glucopyranoside building blocks in YCP was confirmed by the observation that it could be hydrolyzed by the alpha-amylase produced by Bacillus licheniformis. A reliable concentration monitoring experimentation highlighted that the reducing sugars released continuously from YCP during its incubation with the enzyme, and the MW of the main resulting fragment weighed 0.8 x 10(4) Da with approximately 10% of YCP converted to maltose, maltotriose and glucose after a 120-min enzymatic degradation. Finally, YCP was found to be able to increase phagocytic activity of mice in vitro and in vivo, indicating that it may be looked up as a potent immunomodulator that could activate macrophages.

Protection of PC12 cells from hydrogen peroxide-induced injury by EPS2, an exopolysaccharide from a marine filamentous fungus Keissleriella sp. YS4108.

A number of studies indicate that free radicals are involved in the neurodegeneration in Parkinson's and Alzheimer's diseases. EPS2, an exopolysaccharide with a mean molecular weight of 1.3 x 10(5) Da, was isolated by ion-exchange and sizing chromatography from the culture of Keissleriella sp. YS4108, a marine filamentous fungus. Compositionally, it is composed of galactose, glucose, rhamnose, mannose and glucuronic acid in an approximate proportion of 50:8:1:1:0.4. The protective effects of EPS2 on peroxide hydrogen (H2O2)-induced cell lesion, level of lipid peroxidation, antioxidant enzyme activities were investigated in the rat pheochromocytoma line PC12 cells. Following a 1-h exposure of the cells to H2O2, a significant reduction in cell survival and activities of glutathione peroxidase (GSH-Px) and catalase (CAT), as well as increased levels in malondialdehyde (MDA) production and lactate dehydrogenase (LDH) release were observed. However, preincubation of the cells with EPS2 prior to H2O2 exposure elevated the cell survival and GSH-Px and CAT activities, and decreased the level of MDA and LDH activity in a dose-dependent manner. In conclusion, EPS2 possesses pronounced protective effects against H2O2-induced cell toxicity. The finding is of a higher value in searching for new therapeutic agent for treating oxidative damage-derived neurodegenerative disorders.

Identification of a conserved motif in the yeast golgi GDP-mannose transporter required for binding to nucleotide sugar.

Glycoproteins and lipids in the Golgi complex are modified by the addition of sugars. In the yeast Saccharomyces cerevisiae, these terminal Golgi carbohydrate modifications primarily involve mannose additions that utilize GDP-mannose as the substrate. The transport of GDP-mannose from its site of synthesis in the cytosol into the lumen of the Golgi is mediated by the VRG4 gene product, a nucleotide sugar transporter that is a member of a large family of related membrane proteins. Loss of VRG4 function leads to lethality, but several viable vrg4 mutants were isolated whose GDP-mannose transport activity was reduced but not obliterated. Mutations in these alleles mapped to a region of the Vrg4 protein that is highly conserved among other GDP-mannose transporters but not other types of nucleotide sugar transporters. Here, we present evidence that suggest an involvement of this region of the protein in binding GDP-mannose. Most of the mutations that were introduced within this conserved domain, spanning amino acids 280-291 of Vrg4p, lead to lethality, and none interfere with Vrg4 protein stability, localization, or dimer formation. The null phenotype of these mutant vrg4 alleles can be complemented by their overexpression. Vesicles prepared from vrg4 mutant strains were reduced in luminal GDP-mannose transport activity, but this effect could be suppressed by increasing the concentration of GDP-mannose in vitro. Thus, either an increased substrate concentration, in vitro, or an increased Vrg4 protein concentration, in vivo, can suppress these vrg4 mutant phenotypes. Vrg4 proteins with alterations in this region were reduced in binding to guanosine 5'-[gamma-(32)P]triphosphate gamma-azidoanilide, a photoaffinity substrate analogue whose binding to Vrg4-HAp was specifically inhibited by GDP-mannose. Taken together, these data are consistent with the model that amino acids in this region of the yeast GDP-mannose transporter mediate the recognition of or binding to nucleotide sugar prior to its transport into the Golgi.

The endothelin-2/vasoactive intestinal contractor gene: expression and promoter activity in PC12 rat pheochromocytoma cells.

In order to understand the physiological roles of vasoactive intestinal contractor (VIC)/endothelin-2 (ET-2), we examined the expression of this peptide by specific reverse transcriptase polymerase chain reaction (RT-PCR) analysis and found that PC12 rat pheochromocytoma cells express the VIC gene. The 5'-flanking 1.0 kilo base pair (kb) region of the mouse VIC gene is sufficient to express a secreted alkaline phosphatase (SEAP) reporter gene in transiently transfected PC12 cells. The 1.0 kb promoter region may contain cis-acting elements that determine the rate of the VIC gene transcription in PC12 cells.