Structural Aberrations of Cellular Sialic Acids and Their Functions in Cancer Metastases

Sialic acids (neuraminic acids) are a special series of 9 carbon ring negatively charged carbohydrates, which has been found to be selectively changed in malignant cells from structures (both synthesis and structure modifications) to functions (up and down regulation in cells). Sialic acids, in single forms or conjugates, have been systematically studied both in lab and in clinics by GC, GC MS, NMR, HPTLC, HPLC and other modern analytical means. Sialic acids and related conjugates are predicted to be used in cancer diagnosis, cancer prognostic forecasting, designing of cancer chemotherapy regimens, uncovering carcinogenetic processes and neoplasm metastasis. Tumor cell regulative systems and pathways are correlated with sialic acids, which can be applied to prognostic evaluation of cancer patients, and antimetastatic chemotherapy by sialic acid derivatives and analogues. Searching for new biological characteristics of sialic acids in cells have also been extensively studied these days. In this paper, main stream discoveries and advancements are provided , also discussions of possible mechanisms and hypotheses are invoked.

Quantitative analysis of sialic acids in Chinese conventional foods by HPLC-FLD

Background: Sialic acids are a family of ninecarbon sugar compounds with carboxylic acyl derivatives. It exists in bacteria, fish, mammals and other living organisms, participates in and regulates many important life events, such as cell recognition, membrane flow, endocytosis and so on. Sialic acid is usually located in the outermost layer of the sugar part of the cell membrane and the key positions of secreted glycoconjugates (glycolipids, glycoprotein and lipopolysaccharide). Sialic acid (Sia) is an important material foundation for variety of the structure and founction of glycoconjugates. Sia has been known as nearly 50 members, including N-acetylneuraminic acid (Neu5Ac), N-glycoulylneuraminic acid (Neu5Gc) and deaminoneuraminic acid (KDN) as its core monomer. The rest of the sialic acids are derived from these three monomers. The contents of Sia in Chinese food products are unknown. Objective: To determine the contents of Sia in raw and cooked red meat, seafood, poultry and so on. Design: The following food products were purchased from a Chinese supermarket: pork, beef, lamb, salmon, cod, tuna, cow milk, cheese, butter, duck, chicken and chicken eggs. Human milk was collected from Xiamen Maternity and Child Health Care Hospital (Xiamen, China). All tissues were homogenized and hydrolyzed with 0.05 M, 0.1 M and 0.2 M TFA for 150 min at 80°C in dark, respectively. The concentrations of Neu5Ac, Neu5Gc and KDN were determined by using HPLC with fluorescence detector. Results: The contents of total Sia (μg/g tissue or μg/mL liquid sample) in Chinese raw meat were highest in lamb (269.60), followed by pork (254.88), duck (200.63), chicken (162.86) and beef (88.03). The percentages of Neu5Gc were 36.08%, 26.48%, 0%, 0% and 28.40%, respectively. Cod contained higher levels of Sia (171.63) than salmon (104.43) and tuna (77.98). Only Neu5Ac was 50 found in detected aquatic product. Egg yolk contained the highest level of Sia (682.04), and a higher level of Sia (390.67) was found in the egg white. Also our result showed that human milk contained extremely high level of Sia (602.55). Neu5Ac was the predominant form of Sia in all the deteced samples. KDN was found in cow milk only among the samples, the content was 1.14 μg/g. Conclusion: The highest content of Sia in examined Chinese foods was found in 56 eggs, followed by lamb, pork, duck, cod, chicken, salmon, beef and tuna. Knowledge of the Sia content in conventional foods may help us to better understand possible medical disorders involving the uptake of the “non-human” Neu5Gc from our diet.

Blockade of neutrophil recruitment to tumor sites based on sialic acid-modified nanoplatforms enhances the efficacy of checkpoint blockade immunotherapy

Checkpoint inhibitors are designed to rejuvenate depleted or suppressed T cells in the tumor microenvironment,relying on the immune system to control and kill tumors.However,accumulating evidence indicates that tumor-infiltrating neutrophils impede the proliferation and activation of T cells and determine the resistance to checkpoint blockade and chemotherapy.In this study,sialic acid ligand-modified colchicine derivative phospholipid complexes specifically targeted tumor-associated neutrophils in the peripheral blood,blocked neutrophil accumulation in tumors,and attenuated the inhibitory effect of infiltrating neutrophils on T cells.Neutrophil blocking therapy enhanced the immunotherapy effect of the PD-L1 antibody in S180 advanced tumors and 4T1 breast cancer.Our study found that PD-L1 antibody monotherapy increased the tumor infiltration of immunosuppressive neutrophils.Combination therapy with neutrophil blocking can greatly reduce tumor-infiltrating neutrophils and increase the proliferation of cytotoxic CD8^(+) T lymphocytes in the tumor.The combination therapy significantly improved the survival rate of mice with advanced S180 tumors and increased the sensitivity of immune checkpoint inhibitors to 4T1 cold tumors.

Application of sialic acid/polysialic acid in the drug delivery systems

The properties of modified biomaterial are gaining more and more importance in drug delivery systems.Sialic acid(SA)and polysialic acid(PSA)serve as endogenous substances,which are non-immunogenic and biodegradable.At the same time,SA modification of the drugs/carriers can enhance the uptake of tumor cell and retention in brain;PSA modifi-cation can reduce the immunogenicity of the proteins or polypeptides and increase circulation time of the modified drugs/carriers in the blood,thus achieving active targeting effect.These properties offer a variety of opportunities for applications in drug delivery systems.This article summarizes the biological functions of SA and PSA and presents the technologies of SA/PSA modified small molecule drugs,proteins and carriers in drug delivery systems.

ROLE OF SIALIC ACID RESIDUES IN IRON BINDING BY HUMAN LACTOFERRIN

Lactoferrin(Lf-α)is a major constithent of the secondary granules of neutrophils, and is thought to be involved in bacteriostasis through high affinity binding of plasma Fe required for microbial growth.Lf-αis also the major Fe binding protein in milk. Fe bound to Lf-αis available for metabolic use.but the mechanism of Fe release from Lf-αis unknown.Treatment of human Lf-α with neuraminidase to remove sialic acid residues reduced its ability to bind Fe and caused release of Fe already bound to the protein. Reduction in Fe binding capacity was dependent on time of exposure to and concentration of neuraminidase,and was due to Lf-αloss or degradation. Readdition of sialic arid to desialylated Lf -a using a-2, 6-sialyltransferase restored Fe binding.The results suggest that sialylationdesialylation reactions could play a role in physiologic binding and release of Fe from the very high affinity binding sites of Lf -α.

APOPTOSIS OF EPIDIDYMIS EPITHELIUM AND CONTENT OF EPIDIDYMIS SIALIC ACID FOLLOWING TORSED/DETORSED TESTES IN RAT

Objective To investigate the apoptosis of epididyrnis epithelium and the change of epididymissialic acid following torsed/detorsed testes. Methods Twenty four adult male Sprague-Dawley rats were subjected to unilateral 720 testicular torsion with the duration of 2h and 4h, then repaired. The ischemic epididymis were collected for detecting the content of sialic acid by using spectrophotometry and the apoptosis with TUNEL technique. Results There were no statistically significant difference in the apoptosis of epididymis epithelium [(9.51± 2.78)% vs (6.34±1. 98)%] and the content of epididymis sialic acid(23, 3851 ± 9. 2199mg/mgprot vs 19. 3661 6. 3373mg/mgprot) at 24h between following 2h-torsed/detorsed testes and those of sham group. There were statistically significant difference in the apopotosis of epididymis epithelium[ (46. 81 ±3. 55)% vs (6. 34±1. 98) % ] and the content of epididymis sialic acid (13. 7249±7. 8006mg/mgprot vs 19. 3661±6. 3373mg/mgprot) at 24h between following 4h-torsed/detorsed testes and those of sham group(P <0. 05). Conclusion The results suggest that the sialic acid-secreting-function of epididymis remain normal at 24h following 2h-torsed/detorsed testes, while the apoptosis index of epididymis epithelium do not increase. The epididymis would be injured at 24h following 4h-torsed/detorsed testes, while the apoptosis index increased.

SERUM LIPID-BOUND SIALIC ACID IN LUNG CANCER PATIENTS

Serum lipid-bound sialic acid (LSA) assay was evaluated for differential diagnosis between benign and malignant pulmonary disease.Mean serum LSA for normal controls was 13.7±3.7 mg/dl and the upper limit of the normal value was set at 19.8 mg/dl (95% confidence limit,one side).The specificity was 97.l% (95% confidence interval was 93.8%, 100.0%).The mean for benign pulmonary disease was 1 7.l±5.l mg/dl,the specificity was 89.l% (95% confidence interval was 80.9%,97.3%), and the sensitivity was 10.9%.The mean for malignant pulmonary disease was 27.l±7.9 mg/dl, and the sensitivity was 93.3%(95% confidence interval was 88.5%, 98.1%).The serum LSA levels for different malignant pulmonary diseases were different between small cell carcinoma and adenocarcinoma. The results indicate that serum LSA assay might be used as tumor marker to differentiate lung cancer from normal subjects or benign lung disease.

Bitter Melon (Momordica Charantia) Reduces Serum Sialic Acid in Type2 Diabetics: Evidence to Delay the Process of Atherosclerosis

More than 1000 herbal products have been used by diverse cultures of the world to treat hyperglycemia and among them bitter melon (Momordica charantia) is one of the most popular herbal resource. The beneficial effects of bitter melon is not limited to hypoglycaemia only, but it also ameliorates diet induced obesity, insulin resistance and exhibit cardioprotective effects. The present study attempts to investigate the effect of bitter melon fruit juice on a newly investigated risk factor, sialic acid in type2 diabetics. A total of 40 type2 diabetic patients, divided into group A (n = 20) and group B (n = 20) were investigated during the present study. The patients of group A were following bitter melon fruit juice treatment along with diet control, whereas the patients of group B were on diet control only. Serum sialic acid (SSA) decreased in group A from 66.20 ± 2.30 mg/dl to 63.50 ± 2.10 mg/dl (<0.11) but, increased in group B from 66.50 ± 1.70 mg/dl to 68.20 ± 2.50 mg/dl (<0.12), compared to baseline. Post-treatment between group comparison revealed a significant difference (<0.05). The beneficial effects on fasting plasma glucose (FPG) and glycohemoglobin (HbA1-c) were also greater in group A compared to group B as was the case with blood lipids, weight and blood pressure. The study provides another mechanism for the cardioprotective effect of bitter melon and further strengthens its value in the management of type2 diabetes.

Correlation of Cerebrospinal Fluid Sialic Acid with Various Enzymes in Patients with Meningitis

Meningitis is often associated with cerebral compromise which may be responsible for neurological squeal in nearly half of the survivors. Little is known about the mechanisms of Central Nervous System （CNS） involvement in bacterial meningitis. The present study was undertaken to assess the changes in biochemical parameters including glucose, protein, Sialic Acid （SA） and various enzymes like Aspartate Aminotransferase （AST）, Alanine Aminotransferase （ALT）, Creatine Kinase （CK）, Gamma Glutamyltranspeptidase 7 （GGTP） and Lactate Dehydrogenase （LDH） have been determined in the Cerebrospinal Fluid （CSF） of the meningitis patients （n = 26） and compared with control subjects （n = 26）. Total Protein, CK, SA （P 〈 0.02）, AST （P 〈 0.001） and ALT （P 〈 0.0001） of meningitis patients were significantly higher, whereas, glucose （P 〈 0.05） and Gamma Glutamyltranspeptidase （GGT） （P 〈 0.01 and P 〈 0.05, respectively） were significantly lower than those of the controls. This study suggests that loss of integrity of brain-CSF barriers, sialic acid and enzyme profiles may contribute to the severity and neurological complications of meningitis.

New Extracellular Bacillus subtilis Lectins with Sialic Acid-Specificity

The purpose of this work is to perform a detailed study of carbohydrate specificity of the new extracellular bacilli lectins which is considered to determine mechanisms of the lectins action. Sources of lectins were bacterial strains from Ukrainian collection of microorganisms. The optimized protocol of bacilli lectins isolation and purification included precipitation with ammonium sulfate with subsequent gel filtration chromatography on Sepharose CL-6B. Hemagglutinating activity of bacilli lectins and their fine carbohydrate specificity to sialic acids and their derivatives as well as sialic asid-containing and asialic glycoconjugates were studied. The ability of extracellular bacilli lectins to discriminate a- and 13-conformation of carbohydrate molecule and the type of connection between the monomers was determined. Studied lectins showed the most affinity to glycoconjugates containing both types of sialic acids （N-acetylneuraminic acid （Neu5Ac） and N-glycolylneuraminic acid （NeuGc）） and it is supposed to be a basis of their diagnostic and analytical potential.

Siglec-15与CD4^(+)、CD8^(+)在肝细胞癌中的表达关系及其临床意义

目的研究在肝细胞癌(hepatocellutar carcinoma,HCC)中唾液酸免疫球蛋白型凝集素-15(Sialic acid immunoglobulin type lectin 15,Siglec-15)与CD4^(+)、CD8^(+)的表达及相关性,并分析其与临床病理特征及预后的影响。方法通过TCGA数据库分析HCC与正常组织中Siglec-15、CD4^(+)T、CD8^(+)T mRNA的表达水平。收集我院2019年1月至2022年1月行肝癌根治切除术的27例新鲜HCC组织及正常组织标本和56例HCC组织及正常组织石蜡切片标本,qRT-PCR检测Siglec-15和CD4^(+)T、CD8^(+)T mRNA表达水平,IHC检测Siglec-15和CD4^(+)、CD8^(+)蛋白表达水平,并对Siglec-15与CD4^(+)、CD8^(+)蛋白之间的关系及临床病理因素和预后进行分析。结果HCC患者中Siglec-15在HCC组织表达高于正常组织(P<0.05),CD4^(+)、CD8^(+)在HCC组织表达低于正常组织(P<0.05);在HCC组织中,Siglec-15表达与CD4^(+)、CD8^(+)蛋白表达呈负相关(P<0.05)。在HCC组织中,Siglec-15蛋白的表达与患者的TNM分期、肿瘤大小相关(P<0.05),CD4^(+)蛋白的表达与患者的肿瘤大小相关(P<0.05),CD8^(+)蛋白的表达与患者的TNM分期、远处转移相关(P<0.05)。Siglec-15及CD4^(+)的表达与患者的无进展生存期具有相关性(P<0.05)。结论HCC组织中Siglec-15高表达、CD4^(+)、CD8^(+)低表达,且Siglec-15与CD4^(+)、CD8^(+)表达呈负相关。Siglec-15及CD4^(+)的表达高低与HCC患者进展及不良预后相关,可作为预测HCC患者的独立预后因素。

Combined measurement of serum tumor markers in patients with hepatocellular carcinoma

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Serum Contents of Sialic Acids in Mice Bearing Different Tumors

Sialic acids are the derivatives of aminosugar whose parental structures are formed by nine carbons. Recently, the sialic acids have been found to be related to cell malignancy, i.e. the increasing amount of sialic acids on cell membrane, the types of sialic acids, sialyltransferase activity, and sialyltransferase inhibitor can inhibit the tumor metastases. This work tries to explore the tumor-sialic acid relation and the influences of antineoplastic drugs on free sialic acids in mice sera by means of HPLC.

THE ENHANCEMENT OF TWEEN-80 ON THE ANTITUMOR EFFECT OF THE HYPERTHERMIA41℃ IN TUMOR-BEARING MICE

B16 melanoma cells were inoculated into the BALB/C mice to establish melanoma-bearing models. The antitumor effect of Tween-80 in combination with hyperthermia 41℃ was studied. We observed the changes of the mortality of tumor-bearing mice, the tumor growth curves, activities of serum tumor necrosis factor (STNF) and the level of serum sialic acid (SSA) in tumor-bearing mice. The number of pulmonary metastatic tumor foci from blood flow was also detected. The results showed that combined with Twecn-80, hyperthermia 41℃ could dramatically suppress the growth of the melanoma in the feet of mice, survive the tumor-bearing mice and decrease the number of pulmonary metastatic tumor foci but no significant effects were observed by treatment with Tween-80 or hyperthermia at 41℃ alone. The activities of STNF and the level of SSA of the melanoma-bearing mice kept at higher levels than those of normal BALB/C mice. Tween-80 combined with heating 41℃ significantly decreased activities of STNF, but the level of SSA still kept high level within 1 to 2 weeks and decreased 10 weeks later with the tumor regression. These results demonstrate that Tween-80 may make hyperthermia exert effective antitumor effect below the critical temperature and increase the safety of hyperthermia in treatment. It is one of the most ideal synergist with hyperthermia. The changes of STNF and SSA suggest that the synergeticeffect could involve in facilitating the exposure of tumor antigen and activation of immune system.

PROTECTIVE EFFECT OF SHENG MAI SAN ON ADRIAMYCIN-INDUCED CARDIOTOXICITY——AN EXPERIMENTAL STUDY

By measuring the contents of lipid-bound sialic acid (LSA), malonyldialdehyde (MDA), activities of glutathione peroxidase (GSH-px) and superoxide dismutase (SOD) of the myocardial cells, it has been shown that Sheng Mai San can protect the myocardial cells from the adriamycin-induced cardiotoxicity ultrastructrally, inhibit their metabolism of lipid-bound sialic acid and improve the scavenging ability of myocardial cells for semiquinoid free radicals.

Differential Effects of Alternative Glycoforms of IgG on Human Monocytes and Macrophages: Sialylated IgG Induces Novel Expression Signatures of Cell Surface Markers, Cytokines, and Chemokines

The effector functions elicited by the fragment crystallizable (Fc) region of immunoglobulin G (IgG) antibodies are subject to variation by the presence of terminal sialic acid (Sia) residues at asparagine-297 (Asn-297). We have previously shown that the sialic acid-containing (Sia+) fraction of intravenous immune globulin (IVIG) influences cell surface marker expression and cytokine/ chemokine secretion during the differentiation and maturation of human dendritic cells (DC). The present study examined the effects of Sia+ IgG on human peripheral blood mononuclear cell (PBMC)-derived monocyte and macrophage surface marker expression and cytokine/chemokine secretion. Sia+ IgG induced increased expression of CD80 and dendritic cell immunoreceptor (DCIR) on monocytes, whereas the expression of HLA-DR was decreased. In addition, the production of IL-6, TNFα, IL-1β, and CXCL1 by monocytes was profoundly increased by treatment with Sia+ IgG. Sia+ IgG also increased the expression of cell surface markers associated with macrophage polarization (e.g. CD40 and CD206) on monocytes. In macrophage-colony stimulating factor (MCSF) generated macrophages, Sia+ IgG induced increased production of numerous cytokines/ chemokines including IL-6, TNFα, CXCL1, and IL-10, and the expression of the macrophage surface marker CD163. Our data extended prior observations of Sia+ IgG on DC function and showed that Sia+ IgG was able to differentially modulate multiple pathways in monocytes and macrophages. Our data indicate that the Sia+ fraction of IVIG possesses the ability to influence inflammatory processes in multiple immune cell types and induces novel signatures in cell surface marker expression and cytokine/chemokine production.

离子交换树脂法规模化生产乳源酪蛋白糖巨肽及其对流感病毒的血凝抑制活性

目的:优化规模化生产乳源酪蛋白糖巨肽(CGMP)的工艺条件,并探讨其对流感病毒的血凝抑制能力。方法:以阴离子交换树脂为分离介质,唾液酸含量为产品的活性检测指标,分别从上样体积、上样流量、洗脱液浓度、洗脱液体积和树脂使用周期5个工艺条件,在前期小试和中试的基础上,考察从乳清粉中规模化生产CGMP;同时利用血球凝集抑制试验验证产品CGMP对流感病毒的抑制活性。结果:优化的CGMP产品技术路线为上样体积3BV、上样流量0.8 L/min、洗脱体积1BV、洗脱液浓度0.6 mol/L、树脂适宜使用周期4次。该工艺条件下处理乳清粉溶液体积为108 L(2160 g)、树脂36 L,得到CGMP产品21.183 g,得率为0.981 g/100 g,产品纯度为89.032%,回收率为51.972%,唾液酸含量为21.503 g/100 g,蛋白CGMP产品对流感病毒A(H1N1)和流感病毒B的最低抑制质量浓度分别为1.0000,1.2500 mg/mL。结论:利用优化的技术路线生产获得CGMP产品的纯度和唾液酸含量均优于市售商品CGMP,且对流感病毒有明显的抑制作用。

唾液酸结合免疫球蛋白样凝集素-15在食管鳞癌组织中的表达及意义

目的探讨免疫检查点唾液酸结合免疫球蛋白样凝集素-15(Siglec-15)在食管鳞癌中的表达及意义。方法免疫组化检测食管鳞癌组织、癌旁正常食管组织中Siglec-15表达情况,并比较分析其与食管鳞癌患者临床病理特征的关系。结果Siglec-15在食管鳞癌组织中表达阳性率为60.0%(48/80),高于癌旁正常食管组织中的23.75%(19/80)(χ^(2)=21.595,P<0.001)。食管鳞癌组织中Siglec-15蛋白表达与患者肿瘤直径、T分期、TNM分期、N分期及分化程度有关(χ^(2)=7.500,P=0.006;χ^(2)=10.342,P=0.001;χ^(2)=22.547,P=0.016;χ^(2)=20.508,P<0.001;χ^(2)=12.586,P=0.002)。结论Siglec-15在食管鳞癌组织中高表达,与患者的疾病进展显著相关。

唾液酸结合免疫球蛋白样凝集素在细菌感染性疾病中的研究进展

唾液酸结合免疫球蛋白样凝集素(sialic acid-binding immunoglobulin-like lectins,Siglecs)在大多数白细胞上表达,并且在免疫细胞信号传导中起关键作用。最近的研究表明,许多细菌通过唾液酸(sialic acid,Sia)与Siglecs的相互作用来调控宿主免疫应答,影响疾病的发生发展。深入了解细菌致病机制对于破译潜在的有效治疗靶点和帮助人类管理细菌感染性疾病十分重要。本文就Siglecs的结构、生物学功能以及其在细菌感染性疾病中的研究进展作简要综述。

食用燕窝对促进认知影响的定性研究

目的:系统评价燕窝对认知的影响。方法:在中国知网、万方、中国生物医学文献数据库、PubMed和Embase数据库中检索自2012年9月1日—2022年9月1日国内外发表的相关研究文献,并根据纳入排除标准对文献进行筛选。参照SYRCLE动物实验风险评估工具,对相关文献进行综合评价。结果:共纳入5项研究,均为动物模型实验。无论燕窝的来源、给药途径、治疗时间、治疗目的(营养、治疗或预防)是否一致,综述结果都表明,燕窝可以改善实验动物的认知功能,用于诱导性认知功能障碍的治疗,作为子代的认知营养增强剂,对动物暴露于脑毒性物质后续产生的认知损伤具有预防保护作用,且呈现出剂量依赖效应。并且,燕窝的促进认知作用可能与燕窝或其有效成分可以增强抗氧化能力,降低神经炎症和氧化应激反应有关。结论:动物实验表明,燕窝具有促进认知的潜在功效,但因缺乏人群实验,尙无法确定燕窝对人群认知的影响。