Characterization of the chylomicron-remnant-recognition sites on parenchymal and Kupffer cells of rat liver Selective inhibition of parenchymal cell recognition by lactoferrin (original) (raw)
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Lactoferrin specifically inhibits endocytosis of chylomicron remnants but not α-macroglobulin
Journal of Biological Chemistry
Our recently found nonlipoprotein inhibitor of chylomicron remnant uptake, lactoferrin, has been investigated in vivo and in vitro. Lipoprotein lipase extracted triglycerides from chylomicrons, doubly labeled with [3H]retinol/[14C]oleate, in the presence of lactoferrin normally. The subsequent uptake of remnants into liver was retarded considerably. In the intact rat, chylomicron remnants (CRs), predominantly labeled in the apoB48 moiety by 125I, were excluded from the hepatic endosomal compartment in the presence of lactoferrin as shown in subcellular fractionation studies of rat livers. In tissue culture, internalization of [125I]chylomicron remnants was inhibited in the presence of 14 pM lactoferrin by 70%. Upon removal of lactoferrin, internalization was rapidly restored. Protease digestion eliminated the inhibitory effect completely. Modification of arginine residues with cyclohexanedione reversibly removed the inhibitory potency of lactoferrin. We located by molecular modeling...
The Journal of biological chemistry, 1992
Recently it was found that lactoferrin, an iron-binding glycoprotein with a molecular weight of 76,500, inhibits the remnant receptor-mediated uptake of apolipoprotein E (apoE)-bearing lipoproteins by the liver. In the present study we characterized the hepatic recognition of lactoferrin. Intravenously injected 125I-lactoferrin was cleared rapidly from the circulation by the liver (92.8 +/- 9.5% of the dose at 5 min after injection). Parenchymal cells contained 97.1 +/- 1.5% of the hepatic radioactivity. Internalization, monitored by measuring the release of liver-associated radioactivity by the polysaccharide fucoidin, occurred slowly. Only about 40% of the liver-associated lactoferrin was internalized at 10 min after injection, and it took 180 min to internalize 90%. Subcellular fractionation indicated that internalized lactoferrin is transported to the lysosomes. Binding of lactoferrin to isolated parenchymal liver cells was saturable with a dissociation constant of 10 microM (20...
Toxicological Sciences an Official Journal of the Society of Toxicology 2002 68 304 13, 2002
PPAR␣ (peroxisome proliferator activated receptor ␣) is a transcription factor that mediates the rodent liver tumorigenic responses to peroxisome proliferators via regulation of genes that remain to be identified. Using microarray gene expression profiling of mRNA from wild type versus PPAR␣ null mice, we detected a 3-to 7-fold downregulation of hepatic lactoferrin (LF) in response to the PP, diethylhexylphthalate (DEHP; 1150 mg/kg). Northern blot analyses confirmed a significant downregulation of LF mRNA by DEHP in wild type mouse liver. Since LF has been reported to repress tumor necrosis factor-␣ (TNF-␣), LF downregulation by PPs may permit TNF-␣ levels to rise, enhancing hepatocyte survival and proliferation. To test this hypothesis, we asked if exogenous LF could prevent the perturbation of hepatocyte growth by PPs but not by TNF-␣. In vitro, the PPs monoethylhexylphthalate (MEHP; 500 M, the active metabolite of DEHP) and another PP, nafenopin (50 M) or exogenous TNF-␣ (5000 U/ml) induced hepatocyte proliferation and suppressed apoptosis. LF (200 M) blocked the growth but not the peroxisome proliferation response to PPs but could not block the growth response to TNF-␣. Immunocytochemistry using specific antibodies to LF but also to transferrin (TF), a related gene previously shown to contain a PP response element (PPRE), demonstrated that both LF and TF are expressed in murine liver. Furthermore, both were downregulated by DEHP in both wild type and PPAR␣ null mouse liver. These data suggest that the regulation of iron binding proteins by PPAR␣ ligands plays a role in PP-mediated liver growth, but not in peroxisome proliferation.
Biochemical Journal, 1991
The uptake in vivo of chylomicrons and fl-migrating very-low-density lipoprotein (f8-VLDL) by rat liver, which is primarily carried out by parenchymal cells, is inhibited, 5 min after injection, to respectively 35 and 8 % of the control values after preinjection of lactoferrin. The decrease in the uptake of lipoproteins by the liver caused by lactoferrin is a specific inhibition of uptake by parenchymal cells. Competition studies in vitro demonstrate that chylomicron remnants and ,-VLDL compete for the same recognition site on parenchymal cells. Data obtained in vivo together with the competition studies performed in vitro indicate that chylomicron remnants and /3-VLDL interact specifically with the same remnant receptor. Hepatic uptake of '25I-labelleda-macroglobulin in vivo, mediated equally by parenchymal and endothelial cells, is not decreased by preinjection of lactoferrin and no effect on the parenchymal-cell-mediated uptake is found. In vitro, a2-macroglobulin and chylomicron remnants or /3-VLDL show no cross-competition. Culturing of parenchymal cells for 24-48 h leads to a decrease in the cell association of a2-macroglobulin to 26 % of the initial value, while the cell association of ,3-VLDL with the remnant receptor is not influenced. It is concluded that fl-VLDL and chylomicron remnants are recognized by a specific remnant receptor on parenchymal liver cells, while uptake of a2-macroglobulin by liver is carried out by a specific receptor system (presumably involving the LDL-receptor-related protein) which shows properties that are distinct from those of the remnant receptor. Recently, it was shown that LRP and the a-macroglobulin Abbreviations used: LDL, low-density lipoprotein; HDL, high-density lipoprotein; f8-VLDL, f-migrating very-low-density lipoprotein; apoE, apolipoprotein E; LRP, LDL-receptor-related protein; PBS, phosphate-buffered saline (see the Materials and Methods section); DMEM, Dulbecco's modified Eagle medium; 4-APP, 4-aminopyrazolo[3,4-d]pyrimidine. t To whom correspondence should be addressed.
Expression of lactoferrin in human stomach
International Journal of Cancer, 1991
The expression of the haeme-binding protein, lactoferrin, was studied in human gastric tissues displaying normal, benign hyperplastic or malignant histology. A single 2.5-kb mRNA was detected in only 14% (2/14) of normal resections. This was similar to the finding that 85% of tumoun were also negative, with 4/27 positive. In contrast, samples with superficial or atrophic gastritis had a high frequency of expression, with 5/7 and 9 / 14 positive respectively. The higher incidence of lactoferrin mRNA in antral samples was a reflection of the greater proportion of these compared with body resections of patients with gastritis. No expression was seen in any of 5 gastric carcinoma cell lines. High levels were observed in the cardia, in contrast to complete absence in the oesophagus. Immunocytochemistry showed localization of lactoferrin in cells of both antral and body glands. Chief cells, but not adjacent parietal cells, were strongly stained. In tissues exhibiting superficial or atrophic gastritis we observed a greater degree and intensity of staining as compared with samples with normal histology. We also observed some staining of tumour cells, though this was very patchy. Lactoferrin may have a role in mucosal iron transport in both normal and highly proliferating tissue, but does not appear to be significantly associated with malignant lesions.
Lactoferrin-binding sites at the surface of HT29-D4 cells. Comparison with transferrin
European Journal of Biochemistry, 1989
The binding of '251-lactoferrin to HT29-D4 cells, a clone of HT29 cells, was studied and compared to the binding of '"1-transferrin to the same cells. The binding of the two iron-transport proteins is saturable and reversiblc suggesting the presence of specific reccptors for each protein. Scatchard analysis suggests the existence of binding sites for lactoferrin with the relatively high equilibrium dissociation constant, K d l of 408 nM. Additionally, the cell is capable of binding large amounts of lactoferrin with very low affinity, probably in a non-receptor intermediale fashion. The dissociation constant of transferrill and its receptor was calculated 9.29 nM which corresponds well to values found in the literature. In contrast to lactoferrin, the cell was capable of binding only low amounts of transferrin in a non-receptor intermediate fashion. Aftcr chemical crosslinking of lactoferrin to the cell surface, the radiolabeled lactoferrin was found in a complex of molecular inass 300 kDa. Crosslinking of transferrin resulted in a complex of much higher molecular mass.
Role of lactoferrin and its receptors on biliary epithelium
Biometals : an international journal on the role of metal ions in biology, biochemistry, and medicine, 2018
Human lactoferrin is an iron-binding glycoprotein present at high concentrations in breast milk and colostrum. It is produced by many exocrine glands and widely distributed in a variety of body fluids. This protein has antimicrobial, immunomodulatory, antioxidant, and anticancer properties. Two important hLf receptors have been identified: LDL receptor related protein (LRP1), a low specificity receptor, and intelectin-1 (ITLN1), a high specificity receptor. No data are present on the role of hLf on the biliary epithelium. Our aims have been to evaluate the expression of Lf and its receptors in human and murine cholangiocytes and its effect on proliferation. Immunohistochemistry and immunofluorescence (IF) were conducted on human healthy and primary biliary cholangitis (PBC) liver samples as well as on liver samples obtained from normal and bile duct ligated (BDL) mice to evaluate the expression of Lf, LRP1 and ITLN1. Cell proliferation in vitro studies were performed on human cholan...
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1995
and petivenous rat liver parenchymal cells were isolated according to the digitonin-collagenase perfusion method. Affinities and maximal specific binding of a conjugate of glutathione S-transferase and the qmacroglobulin receptor-associated protein (GST-39kDaP), of lactoferrin and of transferrin to freshly isolated periportal parenchymal cells in vitro were not significantly different from values obtained with perivenous cells. It is concluded that the receptors for these three ligands show a zonally homogeneous expression in rat liver. The zonal homogeneity in binding observed for GST-39kDaP is at variance with the 1 _-fold higher periportal over perivenous binding of trypsin-activated cr,-macroglobulin. Since GST-39kDaP as well as trypsin-activated Lu,-macroglobulin are ligands for the cY,-macroglobulin receptor/low-density lipoprotein receptor-related protein, it is suggested that GST-39kDaP can bind to (an) additional receptor(s) with a higher perivenous expression. The zonal homogeneity observed with lactoferrin, an inhibitor of ligand binding to the lipoprotein remnant receptor, may indicate zonal homogeneity of the lipoprotein remnant receptor. The observed zonal homogeneity of the transferrin receptor suggests an equal and essential need for iron by parenchymal cells across the rat liver acinus in vivo. 3 1 7 I 276032. 0005.2760/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0005-2760(95)00060-7