Maternal plasma soluble neuropilin-1 is downregulated in fetal growth restriction complicated by abnormal umbilical artery Doppler: a pilot study.

OBJECTIVES: Placental expression of neuropilin-1 (NRP1), a proangiogenic member of the vascular endothelial growth factor receptor family involved in sprouting angiogenesis, was recently discovered to be downregulated in pregnancies with fetal growth restriction (FGR) and abnormal umbilical artery (UA) Doppler. Soluble NRP1 (sNRP1) is an antagonist to NRP1; however, little is known about its role in normal and FGR pregnancies. This study tested the hypotheses that, first, sNRP1 would be detectable in maternal circulation and, second, its concentration would be upregulated in FGR pregnancies compared to those with normal fetal growth and this would correlate with the severity of the disease as assessed by UA Doppler. METHODS: This was a prospective case-control pilot study of 40 singleton pregnancies (20 FGR cases and 20 uncomplicated controls) between 24 + 0 and 40 + 0 weeks' gestation followed in an academic perinatal center from January 2015 to May 2017. FGR was defined as an ultrasound-estimated fetal weight < 10th percentile for gestational age. The control group was matched to the FGR group for maternal age and gestational age at assessment. Fetal ultrasound biometry and UA Doppler were performed using standard protocols. Maternal plasma sNRP1 measurements were performed using a commercially available ELISA. RESULTS: Contrary to the study hypothesis, maternal plasma sNRP1 levels were significantly decreased in FGR pregnancies as compared to those with normal fetal growth (137.4 ± 44.8 pg/mL vs 166.7 ± 36.9 pg/mL; P = 0.03). However, there was no significant difference in sNRP1 concentration between the control group and FGR pregnancies that had normal UA Doppler. Plasma sNRP1 was downregulated in FGR pregnancies with elevated UA systolic/diastolic ratio (P = 0.023) and those with UA absent or reversed end-diastolic flow (P = 0.005) in comparison to FGR pregnancies with normal UA Doppler. This suggests that biometrically small fetuses without hemodynamic compromise are small-for-gestational age rather than FGR. CONCLUSIONS: This study demonstrated a significant decrease in maternal plasma sNRP1 concentration in growth-restricted pregnancies with fetoplacental circulatory compromise. These findings suggest a possible role of sNRP1 in modulating fetal growth and its potential as a biomarker for FGR. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Characteristics and formation of typical winter haze in Handan, one of the most polluted cities in China.

Handan, a city within the North China Plain (NCP) region, is a typical city influenced by regional particulate matter (PM) pollution. One-year hourly semi-continuous observation was carried out in 2015 in Handan with the aim of identifying the chemical composition and variations in PM2.5. Moreover, the concentration of aerosol precursors, meteorological factors, and secondary transformations are considered. The results demonstrate that the annual average PM2.5 concentration in Handan is 122.35µgm-3, approximately 3.5 times higher than the Chinese National Ambient Air Quality Standard (NAAQS) (35µgm-3), and only 12days were below the guideline. As expected, PM concentrations are highest in winter, especially in December. In addition, we measure the concentrations of five species commonly found in PM, nitrate, sulfate, ammonium, inorganic carbon, and organic carbon. Of these, nitrate and sulfate account for the largest proportion of PM2.5; during periods when the PM2.5 concentration was below 400µgm-3, nitrate dominates, while above this concentration, sulfate dominate. This is likely related to the nitrogen and sulfur oxidation ratios, which are in turn, especially the sulfur oxidation ratio, driven by high relative humidity (>60%). In addition, haze events are driven by other meteorological conditions, wind speed and direction, where low wind speeds from the south and southwest enable pollutant accumulation, which are infrequently interspersed with brief periods with high wind speeds that promote pollutant dispersal. Even though Handan is among the ten most polluted cities in China with regard to air pollution, few studies beyond model simulations have analyzed air pollutant concentrations in this city. Therefore, this study makes a significant contribution to understanding air pollution in Handan, which can further be used to improve our understanding of regional pollution in the highly populated North China Plain. These results have implications for the creation of policies and legislation, as well as other pollution control measures.

Nicotinamide Phosphoribosyltransferase Attenuates Methotrexate Response in Juvenile Idiopathic Arthritis and In Vitro.

Variability in response to methotrexate (MTX) in the treatment of juvenile idiopathic arthritis (JIA) remains unpredictable and poorly understood. Based on previous studies implicating an interaction between nicotinamide phosphoribosyltransferase (NAMPT) expression and MTX therapy in inflammatory arthritis, we hypothesized that increased NAMPT expression would be associated with reduced therapeutic response to MTX in patients with JIA. A significant association was found between increased plasma concentrations of NAMPT and reduced therapeutic response in patients with JIA treated with MTX. Inhibition of NAMPT in cell culture by either siRNA-based gene silencing or pharmacological inhibition with FK-866 was found to result in a fourfold increase in the pharmacological activity of MTX. Collectively, these findings provide evidence that NAMPT inhibits the pharmacological activity of MTX and may represent a predictive biomarker of response, as well as a therapeutic target, in the treatment of JIA with MTX.

Identification of genes and pathways related to lipopolysaccharide signaling in duckling spleens.

Lipopolysaccharide (LPS), the major component of the outer cell wall of Gram-negative bacteria, activates the immune system and threatens the health of livestock and poultry. However, little is known about the genes and pathways involved in the immune response of ducklings to LPS. To elucidate the genes involved in the response of 7-day-old duckling spleens treated with LPS, RNA from LPS-treated and control duckling spleens was analyzed by RNA-Seq. The results showed 11,095 and 10,840 genes with >10 clean reads in the LPS-treated and control groups, respectively. Among these genes, 89 were differentially expressed (log2 ratio ≥ 1, P ≤ 0.01, false discovery rate ≤ 0.001); 67 of these were upregulated and 22 were downregulated in the LPS-treated group compared to the control. GO and GO-rich analysis showed that differentially expressed genes were enriched in 13 functional categories (P < 0.05). Pathway analysis and pathway richness analysis showed that differentially expressed genes were enriched in six pathway categories (P < 0.05). Further analysis showed that some immune system-related signaling pathways, such as the hematopoietic cell lineage, Toll-like receptor signaling pathway, T cell receptor signaling pathway, T cell receptor signaling pathway, complement and coagulation cascades, antigen processing and presentation, and chemokine signaling pathway, are active during the immune response. To confirm the RNA-Seq results, we detected CCL4, LBP, CD71, and STEAP3 expression using real-time PCR analysis, and the results were consistent with the RNA-Seq results. Our results provide new information on the genes involved in the immune response of duckling spleens to LPS.

Selective 14-3-3γ induction quenches p-ß-catenin Ser37/Bax-enhanced cell death in cerebral cortical neurons during ischemia.

Ischemia-induced cell death is a major cause of disability or death after stroke. Identifying the key intrinsic protective mechanisms induced by ischemia is critical for the development of effective stroke treatment. Here, we reported that 14-3-3γ was a selective ischemia-inducible survival factor in cerebral cortical neurons reducing cell death by downregulating Bax depend direct 14-3-3γ/p-ß-catenin Ser37 interactions in the nucleus. 14-3-3γ, but not other 14-3-3 isoforms, was upregulated in primary cerebral cortical neurons upon oxygen-glucose deprivation (OGD) as measured by quantitative PCR, western blot and fluorescent immunostaining. The selective induction of 14-3-3γ in cortical neurons by OGD was verified by the in vivo ischemic stroke model. Knocking down 14-3-3γ alone or inhibiting 14-3-3/client interactions was sufficient to induce cell death in normal cultured neurons and exacerbate OGD-induced neuronal death. Ectopic overexpression of 14-3-3γ significantly reduced OGD-induced cell death in cultured neurons. Co-immunoprecipitation and fluorescence resonance energy transfer demonstrated that endogenous 14-3-3γ bound directly to more p-ß-catenin Ser37 but not p-Bad, p-Ask-1, p-p53 and Bax. During OGD, p-ß-catenin Ser37 but not p-ß-catenin Ser45 was increased prominently, which correlated with Bax elevation in cortical neurons. OGD promoted the entry of 14-3-3γ into the nuclei, in correlation with the increase of nuclear p-ß-catenin Ser37 in neurons. Overexpression of 14-3-3γ significantly reduced Bax expression, whereas knockdown of 14-3-3γ increased Bax in cortical neurons. Abolishing ß-catenin phosphorylation at Ser37 (S37A) significantly reduced Bax and cell death in neurons upon OGD. Finally, 14-3-3γ overexpression completely suppressed ß-catenin-enhanced Bax and cell death in neurons upon OGD. Based on these data, we propose that the 14-3-3γ/p-ß-catenin Ser37/Bax axis determines cell survival or death of neurons during ischemia, providing novel therapeutic targets for ischemic stroke as well as other related neurological diseases.

Effects of polymorphisms and haplotypes within the MSTN gene on duck growth trait.

Abstract 1. Polymorphisms of the duck MSTN gene were investigated in 413 individuals by DNA sequencing and polymerase chain reaction restriction fragment length polymorphism. Four single nucleotide polymorphisms (G129A, C324T, A981G and C1002A), with A981G and C1002A completely linked, were found in the coding region. 2. Association analysis showed that different genotypes of all the identified SNPs were significantly associated with duck growth rate from week 5, 6 and 2 for G129A, C324T and A981G (C1002A), respectively. The greatest difference in body weight was 180 g at week 9, 106 g at week 8 and 123 g at week 8, respectively, for the three SNP's. 3. Linkage disequilibrium (LD) analysis indicated that C324T, A981G and C1002A were in strong LD. Nine main diplotypes from the reconstructed five main haplotypes were observed, and different diplotypes were significantly associated with growth rate from week 1. Birds with the h1h1 diplotype exhibited the largest body weight from week 1 onwards. 4. It was concluded that the duck MSTN gene was associated with body weight and is an important candidate gene for duck growth. traits and marker-assisted selection.

Prevention and treatment of diabetes with resveratrol in a non-obese mouse model of type 1 diabetes.

AIMS/HYPOTHESIS: We recently found that activation of the type III histone deacetylase sirtuin 1 suppresses T cell immune responses. Here we sought to determine the therapeutic potential of the sirtuin 1 activator resveratrol in the treatment of diabetes in the NOD mouse model of type 1 diabetes and the mechanisms underlying such potential. METHODS: NOD mice were fed or subcutaneously injected with resveratrol and evaluated for development of diabetes. Splenocytes from resveratrol-treated and control mice were analysed by gene array. The altered expression of inflammatory genes induced by resveratrol was validated and the role of changed gene expression in prevention of diabetes was determined. RESULTS: Resveratrol administration potently prevented and treated type 1 diabetes in NOD mice. Gene array analysis indicated a dramatic decrease in expression of Ccr6, which encodes chemokine (C-C motif) receptor (CCR) 6, in the splenocytes from resveratrol-treated mice. CCR6 abundance on IL-17-producing cells and CD11b(+)F4/80(hi) macrophages was inhibited by resveratrol treatment. Interestingly, CCR6(+) IL-17-producing cells and CD11b(+)F4/80(hi) macrophages accumulated in the spleens and pancreatic lymph nodes, but their presence in the pancreas was reduced, suggesting that resveratrol blocks their migration from peripheral lymphoid organs to the pancreas. Indeed, the migration of splenocytes toward media containing chemokine (C-C motif) ligand 20 (CCL20) was impaired by resveratrol treatment. CCL20 peptides, which block CCR6 binding to CCL20, inhibited development of type 1 diabetes. CONCLUSIONS/INTERPRETATION: Inhibition of CCR6-mediated migration of inflammatory cells by resveratrol may provide a powerful approach for treatment of type 1 diabetes and possibly of other inflammatory diseases.

[The factors of improving rice transformation efficiency].

The factors influencing the rice transformation frequency have been investigated by using 8 indica and japonica rice cultivars during the transformation procedures, such as induction of calli, selection, and regeneration. The following is the results: The immature embryos were pretreated in 4 degrees C for 4 or 7 days before inoculation, and the regeneration frequency of calli would be increased. High osmotic treatment may increase the possibility of transformation, especially for calli of 6 months or older. The transformation frequency was improved when selection pressure was removed during differentiation period. The V-type selection may be better than the normal selection. There is a difference of differentiation ability among the calli of three periods and it is found that the calli of two or three months are the best for transformation. Proline and DMSO can decrease browning rate of calli.

An HphI polymorphism in the E-selectin gene is associated with premature coronary artery disease.

An increased expression of E-selectin has been observed in the arterial endothelium interacting with lymphocytes and macrophages in human atherosclerotic lesions. We examined whether a polymorphism in the E-selectin gene, due to a G to T mutation (G98T) in the untranslated region of exon 2, was associated with premature coronary artery disease (CAD). Other lipid and nonlipid risk factors including a Ser to Arg (S128R) substitution in the E-selectin gene were also assessed. In patients with premature CAD (men < or = 45 years old and women < or =55 years old, N = 51) who underwent an elective diagnostic coronary arteriography, the frequency of the mutation was significantly higher than in controls (N = 50, 0.22 vs. 0.10, p = 0.024). After controlling for other CAD risk factors (plasma total cholesterol, triglyceride, LDL-apolipoprotein B. cigarette smoking and the S128R mutation) by multiple logistic analysis, the G98T mutation in the E-selectin gene was still a significant predictor of premature CAD [p = 0.022, odds ratio (95%, CI)= 3.58 (1.20-10.67)].

Influence of genetic polymorphisms on responsiveness to dietary fat and cholesterol.

Genes influence quantitative variations in plasma lipoprotein concentrations. For example, intake of dietary saturated fat and cholesterol raises the average serum cholesterol concentration, leading to a higher risk of coronary artery disease in populations. However, not all individuals within the population are susceptible: genetic factors appear to render individuals either "dietary responsive" or "dietary nonresponsive." In this review, we focus on current knowledge about the influence of genetic polymorphisms in certain genes on the lipoprotein response to dietary fat and cholesterol. Our preliminary studies in the Dietary Intervention Study in Children suggest a significant dose-response relation between the decrease in LDL cholesterol from baseline to 36 mo of follow-up in both the intervention group (who consumed a low-fat, low-cholesterol diet) and the usual care group (who consumed a regular diet) and the presence of the APOA1*A allele at the M1 site and the + site at the M2 site of the gene encoding apolipoprotein (apo) A-I. The DNA polymorphisms on the genes encoding apo A-IV, apo B, apo C-III, apo E, lipoprotein lipase, cholesteryl ester transfer protein, lecithin:cholesterol acyltransferase (phosphatidylcholine-sterol O:-acyltransferase), and LDL receptor were found by others to be associated with the plasma lipoprotein response to dietary intervention. Possible mechanisms involved in these effects are discussed and certain discrepancies in the literature about some genetic effects on responsiveness are analyzed. An improved understanding of the influence of specific genes on lipoprotein responsiveness to dietary fat and cholesterol may allow us to identify and counsel certain individuals to avoid high-fat diets so that they may reduce their risk of developing hyperlipidemia and coronary artery disease.

miniSAGE: gene expression profiling using serial analysis of gene expression from 1 microg total RNA.

The use of serial analysis of gene expression (SAGE) to determine gene expression profiles is increasing because the technique can provide absolute transcript numbers in a digital format and identify new genes. We developed a miniSAGE technique, which uses only 1 microg total RNA and reduces the amount of the starting material by 250- to 500-fold. Unlike the other modified SAGE methods, the miniSAGE technique does not require the additional PCR amplifications. The additional PCR amplifications potentially introduce bias and compromise the quantitative aspects of the SAGE method. Three key modifications in the miniSAGE technique are: (i) using the phase lock gel (PLG, Eppendorf) to increase the recovery and the purity of DNA material after each phenol extraction step; (ii) reducing the amount of linkers in the ligation, thereby minimizing their interference with SAGE ditag amplification and increasing the SAGE ditag yield; and (iii) employing the mRNA capture kit (Boehringer Mannheim) to allow the first five steps: mRNA isolation, cDNA synthesis, enzyme cleavage of cDNA, binding of the cleaved biotin-cDNA to the streptavidin-magnetic beads, ligating linkers to the bound cDNA, and the release of cDNA tags to occur within one tube to significantly reduce the loss of material between successive steps. Two fibroblast SAGE libraries have been successfully prepared. The preliminary analysis of 3838 tags from one library demonstrated a typical fibroblast gene expression pattern. This miniSAGE technique will permit a broader application of SAGE.

A PstI polymorphism detects the mutation of serine128 to arginine in CD 62E gene - a risk factor for coronary artery disease.

The mutation of serine128 to arginine in the CD 62E gene is a risk factor for coronary artery disease (CAD). We designed a new method to detect this mutation based on the observation that it is due to a transversion of nucleotide A561 to C, which abolishes a PstI recognition site. Two alleles, A and C, are easily typed when genomic DNA is amplified by PCR, digested with PstI, and separated on agarose gels. Among 153 people who underwent an elective, diagnostic arteriography in Johns Hopkins Hospital, we found that the C allele accounts for 19.5% in angiographically documented CAD patients (n = 82). It is significantly higher than the 10.6% frequency observed in normal controls (n = 71, p < 0.05). It indicates that the C allele is associated with early-onset CAD. This new method should facilitate the screening of this mutant allele in large populations and contribute to the understanding of the molecular mechanism underlying the association of this mutation with CAD.

Screening of Epstein-Barr virus early antigen expression inducers from Chinese medicinal herbs and plants.

Ether extracts of 1693 Chinese medicinal herbs and plants from 268 families were studied for the induction of Epstein-Barr viral (EBV) early antigen (EA) expression in the Raji cell line. Fifty-two from 18 families were found to have inducing activity. Twenty-five and seven of them were from Euphorbiaceae and Thymelaeaeeae, respectively. Some of them, such as Croton tiglium, Euphorbia kansui, Daphne genkwa, Wikstroemia chamaedaphne, Wikstroemia indica, Prunus mandshurica Koehne and Achyranthes bidentata are commonly used drugs. The significance of these herbs in the activation of EBV in vivo and their relation to the development of nasopharyngeal carcinoma were discussed.

Inhibition of apolipoprotein E degradation in a post-Golgi compartment by a cysteine protease inhibitor.

In our prior studies on lipoprotein stimulation of apolipoprotein E (apoE) secretion in HepG2 cells, it became clear that a proportion of the newly synthesized apoE was degraded intracellularly (Ye, S. Q., Olson, L. M., Reardon, C. A., and Getz, G. S. (1992) J. Biol. Chem. 267, 21961-21966). The present study was designed to determine the nature of the proteases and the intracellular sites involved in newly synthesized apoE degradation. The effect of seven protease inhibitors on total apoE levels was examined. Only N-acetyl-leucyl-leucyl-norleucinal (ALLN), a cysteine protease inhibitor, significantly blocked apoE degradation in HepG2 cells. The amount of total apoE from cells chased with ALLN for 4 h was increased by 1.58 +/- 0.05-fold relative to the controls (n = 11, p < 0.01). ALLN extended the half-life of apoE from 2.61 h to 4.38 h (p < 0.01). This effect occurs in a post-Golgi compartment since in the presence of brefeldin A, ALLN had no effect on intracellular apoE levels. Chloroquine and NH4Cl significantly reduced apoE degradation; however, ALLN plus either of these reagents appear to have an additive effect. The amount of apoE in cells chased in Ca(2+)-free medium was significantly higher than that in cells chased in Ca(2+)-containing medium (1.70 +/- 0.07-fold, n = 6, p < 0.01). ALLN plus Ca(2+)-free medium had no additive effect. ALLN had no significant influence on the degradation of albumin but had a similar effect on transfected apoE in Chinese hamster ovary cells. Overall, these data suggest that apoE may be degraded in a post-Golgi compartment of HepG2 and Chinese hamster ovary cells by lysosomal enzymes and cytosolic Ca(2+)-dependent cysteine proteases. ALLN inhibits the latter.

Aurothiolates inhibit HIV-1 infectivity by gold(I) ligand exchange with a component of the virion surface.

Aurothioglucose and aurothiomalate have anti-HIV-1 activity in vitro. Antiviral activity requires the formation of a reactive intermediate with a molar equivalent amount of a thiol ligand. This activates gold(I) ligand exchange between the reactive species bis(thiolato)gold(I) and acidic thiol groups exposed on the surface of proteins. Bis(thioglucose)gold(I) (bisAuTG) which is formed by the reaction of molar equivalent amounts of aurothioglucose and 1-thio-beta-D-glucose completely protected MT-4 and CEM cells against HIV-1NL4-3-induced cytopathogenicity. Although bisAuTG is an inhibitor of human immunodeficiency virus-1 (HIV-1) reverse transcriptase in a cell-free assay, its antiviral effect is due to modification of a surface component of the virion. The HIV-1 strain NL4-3 is 200-fold more sensitive to inhibition of infectivity by bisAuTG than are the strains MN, RF, and SF-2. HIV-1NL4-3 has a unique cysteine residue close to the amino terminus of its gp41 envelope glycoprotein (residue 532 of gp160) which we hypothesize is the target of bisAuTG binding. Mutation of that residue alters HIV-1NL4-3 infectivity and dominantly suppresses virus assembly when coexpressed with the wild-type NL4-3 genome. We show that bisAuTG treatment releases gp120 from the surface of cells expressing wild-type HIV-1NL4-3 envelope glycoprotein, but it does not release gp120 if Cys532 is mutationally altered to Ala. Thus, the antiviral effect of bisAuTG on HIV-1NL4-3 is due to an effect on the association of gp120 with gp41.

Human plasma lipoproteins regulate apolipoprotein E secretion from a post-Golgi compartment.

The molecular regulation of apolipoprotein E (apoE) synthesis and secretion is incompletely understood. In this study, we have examined the effect of human low density lipoprotein (LDL) on apoE mRNA and protein levels in HepG2 and other eukaryotic cells. Exposing HepG2 cells to LDL for times up to 4 h resulted in an increase in 35S-labeled apoE accumulation in the medium by 2.2-fold, relative to serum free controls (n = 10, p < 0.001), with no changes in apoE mRNA levels. Similar observations have been made in JeG-3 cells and Chinese hamster ovary cells stably transfected with human apoE cDNA constructs. These results indicate that the LDL effect operates at a post-transcriptional level. In pulse-chase experiments, the LDL effect on apoE accumulation in the media was observed when it was added only during the chase even in the presence of cycloheximide, indicating that LDL is functioning at a post-translational level. The use of brefeldin A (BFA), an agent that impedes protein transport from the endoplasmic reticulum to the Golgi apparatus, suggests that the LDL effect occurs in a post-Golgi compartment. The addition of protease inhibitors could not duplicate the effects of LDL on the apoE accumulation in the medium. ApoA-I accumulation in the medium of HepG2 cells, but not albumin, was also significantly increased by 1.9-fold (n = 5, p < 0.001).

Plasminogen polymorphism in swine.

1. Plasminogen polymorphism in swine (Sus scrofa) plasma was demonstrated by immunoblotting. 2. Eleven plasminogen phenotypic patterns, including a null pattern, were detected. 3. The null pattern was associated with extremely low plasma triglyceride and increased unesterified cholesterol levels. 4. Changes in plasminogen polymorphic patterns from the fetal to neonate status were observed after nursing commenced.

Tissue distribution of [3H]cholesteryl linoleyl ether-labeled human Lp(a) in different rat organs.

The sites of tissue uptake of human lipoprotein(a) (Lp(a] were studied in rats using [3H]cholesteryl linoleyl ether [( 3H]CLE) as a marker. Since rat plasma has no cholesteryl ester transfer activity, the amount of label in various tissues should reflect the quantitative uptake of Lp(a). Isolated Lp(a) was labeled with [3H]CLE by incubation overnight of Lp(a), a source of cholesteryl ester transfer activity (1.23 g/ml infranate of human plasma), and [3H]CLE-labeled Intralipid. Following labeling, the homogeneity and integrity of Lp(a) was shown by agarose electrophoresis and immunoblotting. Intact Lp(a) was injected via the tail vein of rats (120-170 g, n = 4 at each time point), and tissues were collected at various times thereafter (4-48 h). The disappearance curve of [3H]CLE-labeled Lp(a) from rat plasma was bimodal and had an initial rapid t1/2 of 1.8 h followed by a slower component, t1/2 = 13.3 h. Tissue uptake at all sampling times was greatest in liver (28.5% at 48 h of total dpm injected), followed by the intestine (9-12%), with less than 3% uptake by spleen. The small intestine was divided into four segments, and while the 3H radioactivity was similar in the proximal segments, a time-related increase in [3H]CLE was seen in its most distal portion. These studies indicate that the tissue sites of degradation in the rat of human Lp(a) are similar to human low-density lipoproteins (LDL); the increase in label in the distal portion of the small intestine with time may represent [3H]CLE excreted through the bile and absorbed by the mucosal cells.

Interactions of low density lipoprotein2 and other apolipoprotein B-containing lipoproteins with lipoprotein(a).

Studies were undertaken to investigate potential interactions among plasma lipoproteins. Techniques used were low density lipoprotein2 (LDL2)-ligand blotting of plasma lipoproteins separated by nondenaturing 2.5-15% gradient gel electrophoresis, ligand binding of plasma lipoproteins by affinity chromatography with either LDL2 or lipoprotein(a) (Lp(a)) as ligands, and agarose lipoprotein electrophoresis. Ligand blotting showed that LDL2 can bind to Lp(a). When apolipoprotein(a) was removed from Lp(a) by reduction and ultracentrifugation, no interaction between LDL2 and reduced Lp(a) was detected by ligand blotting. Ligand binding showed that LDL2-Sepharose 4B columns bound plasma lipoproteins containing apolipoproteins(a), B, and other apolipoproteins. The Lp(a)-Sepharose column bound lipoproteins containing apolipoprotein B and other apolipoproteins. Furthermore, the Lp(a) ligand column bound more lipoprotein lipid than the LDL2 ligand column, with the Lp(a) ligand column having a greater affinity for triglyceride-rich lipoproteins. Lipoprotein electrophoresis of a mixture of LDL2 and Lp(a) demonstrated a single band with a mobility intermediate between that of LDL2 and Lp(a). Chemical modification of the lysine residues of apolipoprotein B (apoB) by either acetylation or acetoacetylation prevented or diminished the interaction of LDL2 with Lp(a), as shown by both agarose electrophoresis and ligand blotting using modified LDL2. Moreover, removal of the acetoacetyl group from the lysine residues of apoB by hydroxylamine reestablished the interaction of LDL2 with Lp(a). On the other hand, blocking of--SH groups of apoB by iodoacetamide failed to show any effect on the interaction between LDL2 and Lp(a). Based on these observations, it was concluded that Lp(a) interacts with LDL2 and other apoB-containing lipoproteins which are enriched in triglyceride; this interaction is due to the presence of apolipoprotein(a) and involves lysine residues of apoB interacting with the plasminogen-like domains (kringle 4) of apolipoprotein(a). Such results suggest that Lp(a) may be involved in triglyceride-rich lipoprotein metabolism, could form transient associations with apoB-containing lipoproteins in the vascular compartment, and alter the intake by the high affinity apoB, E receptor pathway.