Biomedical subjects

Xiaoping Zhu

Publications and source records attributed to Xiaoping Zhu.

At least 19 recordsLinked to original sources

PubMed2026

Biomarker Analysis from Patients with Metastatic PDAC Treated with TGFβ Antibody NIS793 plus Abraxane + Gemcitabine versus Abraxane + Gemcitabine Alone in a Phase II, Open-Label, Randomized Study.

PURPOSE: Transforming growth factor β (TGFβ) plays a dual role in cancer, acting as a tumor suppressor early in the disease but promoting progression and immune evasion when dysregulated. In pancreatic ductal adenocarcinoma (PDAC), TGFβ-driven desmoplasia fosters chemoresistance and immunosuppression, limiting therapeutic efficacy. NIS793, a fully human mAb targeting TGFβ, demonstrated antifibrotic and immunomodulatory activity in preclinical models and early-phase trials. PATIENTS AND METHODS: We conducted a randomized, open-label, phase II study in treatment-naïve patients with metastatic PDAC (mPDAC) to evaluate NIS793 ± spartalizumab (anti-PD-1) combined with nab-paclitaxel (or Abraxane)/gemcitabine (ABRA/GEM) versus ABRA/GEM alone. The primary endpoint was progression-free survival (PFS); secondary endpoints included overall survival (OS), safety, pharmacokinetics, and biomarker analyses. Exploratory assessments included paired tumor RNA sequencing, cell-free DNA profiling, and plasma proteomics. RESULTS: NIS793 demonstrated target engagement and suppression of TGFβ signaling, confirmed by transcriptomic and proteomic analyses. Stromal remodeling was evident, with significant downregulation of cancer-associated fibroblast markers (Acta2, Fap) and collagen-related signatures. Despite proof of mechanism, clinical efficacy was not observed: Median PFS and OS were comparable or numerically worse in the NIS793 arm versus control (HR for OS in NIS793 + ABRA/GEM vs. ABRA/GEM: 1.32; 95% confidence interval, 0.84-2.07). The safety profile was manageable, with no unexpected toxicities. Biomarker data revealed increased expression of neutrophil-related genes after treatment, suggesting potential induction of tumor-promoting inflammation. CONCLUSIONS: NIS793 effectively inhibited TGFβ signaling and led to stromal remodeling but failed to improve outcomes in mPDAC. These findings highlight the complexity of TGFβ biology and caution against its blockade in combination with chemotherapy for PDAC. Future strategies should consider context-dependent effects of TGFβ inhibition.

Humans↗

PubMed2006

Nitric oxide modulates neuromuscular transmission during hypoxia in rat diaphragm.

Hypoxia impairs neuromuscular transmission in the rat diaphragm. In previous studies, we have shown that nitric oxide (NO) plays a role in force modulation of the diaphragm under hypoxic conditions. The role of NO, a neurotransmitter, on neurotransmission in skeletal muscle under hypoxic conditions is unknown. The effects of the NO synthase (NOS) inhibitor nomega-nitro-L-arginine (L-NNA, 1 mM) and the NO donor spermine NONOate (Sp-NO, 1 mM) were evaluated on neurotransmission failure during nonfatiguing and fatiguing contractions of the rat diaphragm under hypoxic (PO2 approximately 5.8 kPa) and hyperoxic conditions (PO2 approximately 64.0 kPa). Hypoxia impaired force generated by both muscle stimulation at 40 HZ (P40M) and by nerve stimulation at 40 HZ (P40N). The effect of hypoxia in the latter was more pronounced. L-NNA increased P40N whereas Sp-NO decreased P40N during hypoxia. In contrast, neither L-NNA nor Sp-NO affected P40N during hyperoxia. L-NNA only slightly reduced neurotransmission failure during fatiguing contractions under hyperoxic conditions. Consequently, neurotransmission failure assessed by comparing force loss during repetitive nerve simulation and superimposed direct muscle stimulation was more pronounced in hypoxia, which was alleviated by L-NNA and aggravated by Sp-NO. These data provide insight in the underlying mechanisms of hypoxia-induced neurotransmission failure. This is important as respiratory muscle failure may result from hypoxia in vivo.

Animals↗

PubMed2006

Human Streptococcus suis outbreak, Sichuan, China.

From mid-July to the end of August 2005, a total of 215 cases of human Streptococcus suis infections, 66 of which were laboratory confirmed, were reported in Sichuan, China. All infections occurred in backyard farmers who were directly exposed to infection during the slaughtering process of pigs that had died of unknown causes or been killed for food because they were ill. Sixty-one (28%) of the farmers had streptococcal toxic shock syndrome; 38 (62%) of them died. The other illnesses reported were sepsis (24%) and meningitis (48%) or both. All isolates tested positive for genes for tuf, species-specific 16S rRNA, cps2J, mrp, ef, and sly. A single strain of S. suis caused the outbreak, as shown by the identification of a single ribotype. The high death ratio was of concern; prohibiting backyard slaughtering ended the outbreak.

Adult↗

PubMed2006

Streptococcus suis sequence type 7 outbreak, Sichuan, China.

An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described.

Animals↗

PubMed2005

Gene therapy with iNOS provides long-term protection against myocardial infarction without adverse functional consequences.

Previous studies have shown that gene therapy with inducible nitric oxide synthase (iNOS) protects against myocardial infarction at 3 days after gene transfer. However, the long-term effects of iNOS gene therapy on myocardial ischemic injury and cardiac function are unknown. To address this issue, we used a recombinant adenovirus 5 (Ad5) vector (Av3) with deletions of the E1, E2a, and E3 regions, which enables long-lasting recombinant gene expression for at least 2 mo due to lack of inflammation. Mice received intramyocardial injections in the left ventricular (LV) anterior wall of Av3/LacZ (LacZ group) or Av3/iNOS (iNOS group); 1 or 2 mo later, they were subjected to myocardial infarction (30-min coronary occlusion followed by 4 h of reperfusion). Cardiac iNOS gene expression was confirmed by immunoblotting and activity assays at 1 and 2 mo after gene transfer. In the iNOS group, infarct size (percentage of risk region) was significantly reduced (P < 0.05) both at 1 mo (24.2 +/- 3.4%, n = 6, vs. 48.0 +/- 3.6%, n = 8, in the LacZ group) and at 2 mo (23.4 +/- 3.1%, n = 8, vs. 36.6 +/- 2.4%, n = 7). The infarct-sparing effects of iNOS gene therapy were as powerful as those observed 24 h after ischemic preconditioning (23.1 +/- 3.4%, n = 10). iNOS gene transfer had no effect on LV function or dimensions up to 8 wk later (echocardiography). These data demonstrate that iNOS gene therapy mediated by the Av3 vector affords long-term (2 mo) cardioprotection without inflammation or adverse functional consequences, a finding that provides a rationale for further preclinical testing of this therapy.

Animals↗

PubMed2005

Microglia Kv1.3 channels contribute to their ability to kill neurons.

Many CNS disorders involve an inflammatory response that is orchestrated by cells of the innate immune system: macrophages, neutrophils, and microglia (the endogenous CNS immune cell). Hence, there is considerable interest in anti-inflammatory strategies that target these cells. Microglia express Kv1.3 (KCNA3) channels, which we showed previously are important for their proliferation and the NADPH-mediated respiratory burst. Here, we demonstrate the potential for targeting Kv1.3 channels to control CNS inflammation. Rat microglia express Kv1.2, Kv1.3, and Kv1.5 transcripts and protein, but only a Kv1.3 current was detected. When microglia were activated with lipopolysaccharide or a phorbol ester, only the Kv1.3 transcript (but not protein) expression changed. Using a Transwell cell-culture system that allows separate drug treatment of microglia or neurons, we found that activated microglia killed postnatal hippocampal neurons through a process that requires Kv1.3 channel activity in microglia but not in neurons. A major neurotoxic molecule in this model was peroxynitrite, which is formed from superoxide and nitric oxide; thus, it is significant that Kv1.3 channel blockers reduced the respiratory burst, but not nitric oxide production, by the activated microglia. In addressing the biochemical pathway affected by Kv1.3 channel activity, we found that Kv1.3 acts via a different cellular mechanism from the broad-spectrum drug minocycline, which is often used in animal models of neuroinflammation. That is, the dose-dependent reduction in neuron killing by minocycline corresponded with a reduction in p38 mitogen-activated protein kinase activation in microglia; however, none of the Kv1.3 blockers affected p38 activation.

Animals↗

PubMed2005

Calnexin and ERp57 facilitate the assembly of the neonatal Fc receptor for IgG with beta 2-microglobulin in the endoplasmic reticulum.

The neonatal FcR (FcRn) consists of an MHC class I-like H chain in noncovalent association with beta(2)-microglobulin (beta(2)m). The proper folding of FcRn in the endoplasmic reticulum is essential for FcRn function. Using a low stringency immunoprecipitation of human FcRn, we observed the coprecipitation of an 88-kDa band. Mass spectrometry analysis revealed that this band was identical with calnexin (CNX). This association was verified by Western blotting the CNX or FcRn immunoprecipitates with either an anti-FcRn or anti-CNX Ab. In the beta(2)m-null FO-1 cell transfected with FcRn H chain alone or both FcRn H chain and beta(2)m, CNX bound to the FcRn H chain before the FcRn H chain association with beta(2)m. However, calreticulin only bound to the FcRn H chain-beta(2)m complex. Furthermore, the thiol oxidoreductase ERp57 was detected in FcRn-CNX complexes, suggesting its role in disulfide bond formation of the FcRn H chain. Removal of the N-linked glycosylation site from the FcRn H chain resulted in a decreased association of the FcRn H chain for beta(2)m. However, the absence of CNX did not significantly affect FcRn assembly as defined by the ability of FcRn to bind IgG and exit to the cell surface. This suggests that other chaperones compensate for the function of CNX in FcRn assembly. In addition, we found that tapasin and TAP were not involved in FcRn assembly, as shown by coimmunoprecipitation in THP-1 cells and IgG-binding assays in 721.220 (tapasin-deficient) and 721.174 (TAP-deficient) cells transfected with FcRn. These findings show the importance of chaperones in FcRn assembly.

Amino Acid Sequence↗

PubMed2005

Late preconditioning induced by NO donors, adenosine A1 receptor agonists, and delta1-opioid receptor agonists is mediated by iNOS.

Although ischemia-induced late preconditioning (PC) is known to be mediated by inducible nitric oxide (NO) synthase (iNOS), the role of this enzyme in pharmacologically induced late PC remains unclear. We tested whether targeted disruption of the iNOS gene abrogates late PC elicited by three structurally different NO donors [diethylenetriamine/NO (DETA/NO), nitroglycerin (NTG), and S-nitroso-N-acetyl-penicillamine (SNAP)], an adenosine A1 receptor agonist [2-chloro-N6-cyclopentyladenosine (CCPA)], and a delta1-opioid receptor agonist (TAN-670). The mice were subjected to a 30-min coronary occlusion followed by 24 h of reperfusion. In iNOS knockout (iNOS-/-) mice, infarct size was similar to wild-type (WT) controls, indicating that iNOS does not modulate infarct size in the absence of PC. Pretreatment of WT mice with DETA/NO, NTG, SNAP, TAN-670, or CCPA 24 h before coronary occlusion markedly reduced infarct size. In iNOS-/- mice, however, the late PC effect elicited by DETA/NO, NTG, SNAP, TAN-670, and CCPA was completely abrogated. Furthermore, in WT mice pretreated with TAN-670 or CCPA, the selective iNOS inhibitor 1400W also abolished the delayed PC properties of these drugs; 1400W had no effect in WT mice. These data demonstrate that iNOS plays an obligatory role in NO donor-induced, adenosine A1 receptor agonist-induced, and delta1-opioid receptor agonist-induced late PC, underscoring the critical role of this enzyme as a common mediator of cardiac adaptations to stress.

Adenosine↗

PubMed2005

Four-phase single-capillary stepwise model for kinetics in arterial spin labeling MRI.

An extended model for extracting measures of brain perfusion from pulsed arterial spin labeling (ASL) data while considering transit effects and restricted permeability of capillaries to blood water is proposed. We divided the time course of the signal difference between control and labeled images into four phases with respect to the arrival time of labeled blood water at the voxel of interest (t(A)), transit time through the arteries in the voxel (t(ex)), and duration of the bolus of labeled spins (tau). Dividing the labeled slab of blood water into many discrete segments, and adapting numerical integration methods allowed us to conveniently model restricted capillary-tissue exchange based on a modified distributed parameter model. We compared this four-phase single-capillary stepwise (FPSCS) model with models that treat water as a freely diffusible tracer, using both simulations and experimental ASL brain imaging data at 1.5T from eight healthy subjects (24-80 years old). The FPSCS model yielded less errors in the least-squares sense in fitting brain ASL data in comparison with freely diffusible tracer models of water (P = 0.055). These results imply that restricted permeability of capillaries to water should be considered when brain ASL data are analyzed.

Adult↗

PubMed2005

Column-mode phosphate removal by a novel highly selective adsorbent.

A phosphoric acid resin RGP was immobilized with zirconium(IV) (Zr(IV)) to investigate its applicability in phosphate removal. When loaded with Zr(IV), RGP was changed into an effective ligand exchanger with phosphate sorption capacity of 0.345 mmol/ml. Little metal leakage was observed. Breakthrough of phosphate sorption depended on solution acidity and phosphate concentration. An increase of solution pH greatly suppressed phosphate removal, but even at pH 8.21, about 56% of the added phosphate (2.8mM) in the feed solution could still be sorbed. Electrolytes in the aqueous solution did not interfere with phosphate sorption; on the contrary, an enhancement effect was observed. Due to the high sorption capacity of Zr(IV)-loaded RGP, low concentration of phosphate can be removed at high flow rate (100 h(-1) in space velocity). The sorbed phosphate on the Zr(IV)-loaded RGP could be quantitatively eluted with 0.5M sodium hydroxide solution. The Zr(IV)-loaded RGP is a promising ligand exchanger for treating wastewater containing trace amounts of inorganic phosphate.

Adsorption↗

PubMed2004

Administration of a CO-releasing molecule induces late preconditioning against myocardial infarction.

Mounting evidence suggests that carbon monoxide (CO) exerts powerful cytoprotective actions. CO-releasing molecules (CORMs) offer an effective means of delivering CO to tissues in vivo. The goal of the present study was to determine whether a water-soluble CORM, tricarbonylchloro(glycinato)ruthenium(II) (CORM-3), induces delayed protection against myocardial infarction 24 h later and to explore the duration of this protection. Mice received a 60-min i.v. infusion of CORM-3 or inactive CORM-3 (which does not release CO) and then, 24, 72, or 120 h later, underwent a 30-min coronary occlusion followed by 24 h of reperfusion. Pretreatment with CORM-3 24 h prior to coronary occlusion markedly reduced infarct size (24.8% +/- 2.9% of the risk region vs. 43.8% +/- 4.4% with inactive CORM-3). The infarct-sparing effect of CORM-3 was still evident 72 h after administration of the CO donor (20.4% +/- 3.7% of the risk region vs. 41.9% +/- 2.5% with inactive CORM-3) but was no longer apparent at 120 h. Both at 24 and 72 h, the protective effects of CORM-3 were equivalent to those afforded by the late phase of ischemic preconditioning (PC; 27.0% +/- 2.9% and 30.3% +/- 3.9% of the risk region, respectively). We conclude that the novel CO-releasing compound, CORM-3, induces delayed protection against myocardial infarction which is similar to that afforded by the late phase of ischemic PC, and that this salubrious effect is sustained for 72 h. To our knowledge, this is the first report that exposure to CO causes the heart to shift to a preconditioned phenotype. In addition, this study provides the first evidence that the cardioprotective actions of ischemic PC persist for 72 h in the mouse.

Animals↗

PubMed2004

Hypoxia-induced dysfunction of rat diaphragm: role of peroxynitrite.

Oxidants may play a role in hypoxia-induced respiratory muscle dysfunction. In the present study we hypothesized that hypoxia-induced impairment in diaphragm contractility is associated with elevated peroxynitrite generation. In addition, we hypothesized that strenuous contractility of the diaphragm increases peroxynitrite formation. In vitro force-frequency relationship, isotonic fatigability, and nitrotyrosine levels were assessed under hypoxic (Po(2) approximately 6.5 kPa) and hyperoxic (Po(2) approximately 88.2 kPa) control conditions and also in the presence of authentic peroxynitrite (60 min), ebselen (60 min), and the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine acetate (L-NMMA) (90 min). A hypoxia-induced downward shift of the force-frequency relationship was associated with elevated nitrotyrosine level in the diaphragm. During hypoxia, both ebselen and L-NMMA decreased nitrotyrosine levels but did not affect force generation. Strenuous contractions impaired force generation but did not affect nitrotyrosine levels in the diaphragm during hypoxia. But under hyperoxic conditions, fatiguing contractions were associated with elevated diaphragm nitrotyrosine levels. Under hyperoxic conditions exogenous peroxynitrite impaired force generation and increased nitrotyrosine level. These studies show that hypoxia-induced impairment in diaphragm contractility is associated with increased diaphragm protein nitration, but no causal relationship was found between diaphragm nitrotyrosine formation and in vitro force generation.

Animals↗

PubMed2004

Administration of a CO-releasing molecule at the time of reperfusion reduces infarct size in vivo.

Although carbon monoxide (CO) has traditionally been viewed as a toxic gas, increasing evidence suggests that it plays an important homeostatic and cytoprotective role. Its therapeutic use, however, is limited by the side effects associated with CO inhalation. Recently, transition metal carbonyls have been shown to be a safe and effective means of transporting and releasing CO groups in vivo. The goal of the present study was to test whether a water-soluble CO-releasing molecule, tricarbonylchloro(glycinato) ruthenium (II) (CORM-3), reduces infarct size in vivo when given in a clinically relevant manner, i.e., at the time of reperfusion. Mice were subjected to a 30-min coronary artery occlusion followed by 24 h of reperfusion and were given either CORM-3 (3.54 mg/kg as a 60-min intravenous infusion starting 5 min before reperfusion) or equivalent doses of inactive CORM-3, which does not release CO. CORM-3 had no effect on arterial blood pressure or heart rate. The region at risk did not differ in control and treated mice (44.5 +/- 3.5% vs. 36.5 +/- 1.6% of the left ventricle, respectively). However, infarct size was significantly smaller in treated mice [25.8 +/- 4.9% of the region at risk (n = 13) vs. 47.7 +/- 3.8% (n = 14), P < 0.05]. CORM-3 did not increase carboxyhemoglobin levels in the blood. These results suggest that a novel class of drugs, CO-releasing molecules, can be useful to limit myocardial ischemia-reperfusion injury in vivo.

Animals↗

PubMed2004

Tumor necrosis factor-alpha does not modulate ischemia/reperfusion injury in naïve myocardium but is essential for the development of late preconditioning.

The role of tumor necrosis factor (TNF)-alpha in myocardial ischemia/reperfusion injury remains controversial. We used homozygous TNF-alpha null mice (TNF-alpha(-/-)) to determine whether TNF-alpha modulates myocardial ischemia/reperfusion injury. Mice were subjected to a 30-min coronary occlusion followed by 24 h of reperfusion. When wild-type mice were preconditioned with six cycles of 4-min coronary occlusion/4-min reperfusion 24 h before the 30-min occlusion, infarct size was reduced from 58.6 +/- 1.9% of the risk region to 19.3 +/- 3.6%, indicating a late preconditioning (PC) effect. In non-preconditioned TNF-alpha(-/-) mice, infarct size was similar to that observed in wild-type mice (55.5 +/- 3.7%). However, in TNF-alpha(-/-) mice preconditioned with six occlusion/reperfusion cycles 24 h earlier, infarct size was not reduced (55.2 +/- 5.7%), indicating that the late PC protection against infarction was completely abolished. While minimal TNF-alpha immunoreactivity was detected in sham-operated hearts, extensive TNF-alpha expression was noted in the cytoplasm of cardiomyocytes in the ischemic/reperfused region 30 min after the PC ischemia. At 30 min after PC, wild-type mice exhibited increased DNA-binding activity of nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1) and nuclear translocation of p65, c-Jun and c-Fos; all of these changes were absent in TNF-alpha(-/-) mice. These data demonstrate that TNF-alpha does not modulate infarct size in the naïve (non-preconditioned) state but is essential for the development of the late phase of ischemic PC, possibly via the activation of NF-kappa B and AP-1 transcription factors.

Active Transport, Cell Nucleus↗

PubMed2004

Effects of conjugated linoleic acid levels and feeding intervals on performance, carcass traits and fatty acid composition of finishing barrows.

Two experiments were conducted to investigate the effects of dietary conjugated linoleic acid (CLA) on performance, carcass traits, fatty acid composition and subcutaneous adipose tissue cellularity in finishing barrows. In Experiment 1, 54 crossbred barrows were allotted to one of three treatments, with six pens per treatment and three barrows in each pen. The pigs were fed a diet containing 0, 2, or 4% CLA oil for 6 weeks. Daily gain (P < 0.01) and feed efficiency (P < 0.01) improved with dietary CLA. Loin muscle area (P = 0.01) and intramuscular fat (P = 0.01) increased while 10th rib fat (P = 0.03) and last rib fat (P = 0.02) thickness decreased with increasing dietary CLA. Total CLA isomers increased (P < 0.01) with increasing dietary CLA. Myristic, palmitic and stearic acid levels were increased while oleic, linoleic, linolenic and arachidonic acid decreased in loin muscle and subcutaneous adipose tissue. In Experiment 2, barrows (n = 54) were allotted to one of two treatments with nine pens per treatment and three pigs in each pen. Pigs were fed a diet supplemented with 4% CLA for 3 or 6 weeks before slaughter. Over the entire experimental period, daily gain and feed efficiency were higher (P < 0.01) when CLA was fed for a longer period. Loin muscle area (P < 0.01) and intramuscular fat (P < 0.01) increased while backfat thickness at the 10th (P = 0.03) and last rib (P = 0.04) decreased when CLA was fed for 6 vs. 3 weeks. The number of cells in subcutaneous adipose tissue was not affected while adipocyte volume decreased (P = 0.01) with longer feeding time on dietary CLA. The increased CLA content of pork from CLA fed pigs provides the pork industry with an opportunity to provide value-added, healthful meat products for human consumption with respect to CLA intake and potential improvements in human health.

Adipose Tissue↗

PubMed2004

Effect of cDNA fragments in different length derived from potato virus Y coat protein gene on the induction of RNA-mediated virus resistance.

We have reported that cDNA derived from entire coat protein (CP) gene of potato virus Y (PVY) could induce resistance to PVY infection in transgenic tobacco plants, and the resistance was further demonstrated to be RNA-mediated rather than coat protein-mediated. In this study, we cloned cDNA fragments of 202 bp, 417 bp, and 603 bp in length derived from the 3' end of the PVY CP gene, and the cDNA fragments were introduced into tobacco (var. NC89) plants via Agrobacterium-mediated transformation system. The results of resistance assay showed that the CP cDNA fragments of 417 bp and 603 bp could confer resistance of the transgenic plants to PVY infection, but the fragment of 202 bp in length could not. Molecular analysis revealed that the resistance was RNA-mediated, which is believed to be a result of post-transcriptional gene silencing. The results indicate that the length of cDNA fragments needed for resistance induction was located somewhere between 202 bp and 417 bp from the 3' end of PVY CP gene.

Blotting, Northern↗

PubMed2003

Functional expression of the multidrug resistance protein 1 in microglia.

Brain expression of the multidrug resistance proteins (MRPs), a collection of membrane-associated ATP-dependent efflux transporters, is poorly understood. Although several studies have examined the expression of these proteins within the brain barriers (i.e., the blood-brain barrier and choroid plexus), little information is available with respect to brain parenchyma cells such as microglia and astrocytes. Because microglia are the primary brain cells infected by the human immunodeficiency virus type 1 (HIV-1), MRP1 expression within microglia may contribute to lower brain accumulation of anti-HIV drugs. To examine the expression pattern of MRP1 within microglia, we performed reverse transcriptase-polymerase chain reaction analysis and Western blotting on a rat brain microglia cell line MLS-9, and in primary cultures of rat microglia. Both rat MRP1 (rMPR1) mRNA and protein were expressed in the cell line, as well as the primary cultures. We then characterized rMRP1-mediated transport properties in MLS-9 cells using [3H]vincristine, a known MRP1 substrate. Vincristine accumulation by monolayers of MLS-9 cells increased significantly in the presence of several well established MRP1 inhibitors (MK571, genistein, sulfinpyrazone, probenecid, and indomethacin), protease inhibitors, or the ATPase inhibitor sodium azide. In addition, vincristine accumulation was significantly modulated by altering the intracellular concentration of the reduced form of glutathione, further suggesting the involvement of rMRP1-mediated transport. These results provide strong evidence that the MRP1 protein is both expressed and functional in microglia cells. They also suggest that brain parenchyma can act as a "second" barrier to drug permeability and regulate brain distribution/accumulation of various xenobiotics, including protease inhibitors.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Anti-nutritional effects of a moderate dose of soybean agglutinin in the rat.

This study was conducted to investigate the effects of a moderate dose of purified soybean agglutinin on performance and nitrogen digestibility in rats as well as to determine its effects on the protein, DNA and RNA content of the small intestine and pancreas. Twenty-four Sprague-Dawley rats were randomly allotted into one of four groups for a 10-day nitrogen balance experiment. The four groups of rats were fed 7 g of a casein-cornstarch based diet or a similar diet supplemented with 0.1, 0.2 or 0.4 mg/g purified soybean agglutinin. All experimental diets were adjusted to an identical nutrient level. Dose of soybean agglutinin had no significant effect on rat performance. Incorporation of soybean agglutinin in the diet reduced apparent protein digestibility and the utilization of dietary protein by increasing nitrogen loss from the faeces and urine. Fresh pancreatic weight increased in rats fed soybean agglutinin at a level of 0.4 mg/g in the diet compared to the control, but the dry pancreatic weight and the protein content of the pancreas did not differ among the four groups. However the DNA and RNA content of the pancreas had a tendency to increase with a higher level of soybean agglutinin. The weight of the jejunum and its protein, DNA and RNA content were not significantly affected by soybean agglutinin, but the dry weight and the RNA of the jejunum tended to increase with higher levels of soybean agglutinin in the diet. In conclusion, purified soybean agglutinin, at moderate levels in the rats diet, had negative effects on digestive function, such as nitrogen digestibility, nitrogen retention and nitrogen balance. As the level of soybean agglutinin increased, the effects became more pronounced. Meanwhile, hypertrophy of the pancreas was observed with higher doses of soybean agglutinin incorporation in the diets.

Animal Feed↗