Systemic blockade of the hyaluronan receptor for endocytosis prevents lymph node metastasis of prostate cancer

Tumor progression and metastasis are promoted by the remodeling of organized tissue architecture and engagement of molecular interactions that support tumor cell passage through endothelial barriers. Prostate tumor cells that secrete and turn over excessive quantities of pericellular hyaluronan (HA) exhibit accelerated growth kinetics and spontaneous lymph node metastasis in mice. The HA receptor for endocytosis (HARE) is an endocytic clearance receptor for HA in the liver that is also highly expressed in sinusoidal endothelium of lymph nodes and bone marrow, which are frequent sites of prostate cancer metastasis. In our study, we tested the hypothesis that HARE can act as an endothelial receptor for metastatic tumor cells with pericellular HA. In an orthotopic mouse model of prostate cancer, we delivered a monoclonal antibody against HARE that specifically blocks HA binding and internalization. This treatment fully blocked the formation of metastatic tumors in lymph nodes. No effects on primary tumor growth were observed and the antibody did not induce toxic outcomes in any other tissue. Our results implicate HARE for the first time in potentiation of tumor metastasis and suggest a novel mechanism by which tumor cell-associated HA could promote tissue-specific dissemination. "Published 2012 Wiley Periodicals, Inc. This article is a US Government work, and, as such, is in the public domain in the United States of America."

The cytoplasmic domain of the hyaluronan receptor for endocytosis (HARE) contains multiple endocytic motifs targeting coated pit-mediated internalization

The hyaluronic acid (HA) receptor for endocytosis (HARE) is the primary scavenger receptor for HA and chondroitin sulfates in mammals. The two human isoforms of HARE (full-length 315-kDa and a 190-kDa proteolytic cleavage product), which are type I single-pass membrane proteins, are highly expressed in sinusoidal endothelial cells of lymph nodes, liver, and spleen. Their identical HARE cytoplasmic domains contain four candidate AP-2/clathrin-mediated endocytic signaling motifs as follows: YSYFRI(2485), FQHF(2495), NPLY(2519), and DPF(2534) (315-HARE numbering). Stably transfected cells expressing 190-HARE(DeltaYSYFRI), 190-HARE(DeltaFQHF), or 190-HARE(DeltaNPLY) (lacking Motifs 1, 2, or 3) had decreased (125)I-HA endocytosis rates of approximately 49, approximately 39, and approximately 56%, respectively (relative to wild type). In contrast, 190-HARE(DeltaDPF) cells (lacking Motif 4) showed no change in HA endocytic rate. Deletions of motifs 1 and 2 or of 1, 2, and 4 decreased the rate of HA endocytosis by only approximately 41%. Endocytosis was approximately 95% decreased in mutants lacking all four motifs. Cells expressing a 190-HARE(Y2519A) mutant of the NPLY motif retained 85-90% of wild type endocytosis, whereas this mutation in the triple motif deletant decreased endocytosis to approximately 7% of wild type. Tyr in NPLY(2519) is thus important for endocytosis. All HARE mutants showed similar HA binding and degradation of the internalized HA, indicating that altering endocytic motifs did not affect ectodomain binding of HA or targeting of internalized HA to lysosomes. We conclude that, although NPLY may be the most important motif, it functions together with two other endocytic motifs; thus three signal sequences (YSYFRI, FQHF, and NPLY) provide redundancy to mediate coated pit targeting and endocytosis of HARE.

The human hyaluronan receptor for endocytosis (HARE/Stabilin-2) is a systemic clearance receptor for heparin

The hyaluronic acid receptor for endocytosis (HARE; also designated Stabilin-2) mediates systemic clearance of hyaluronan and chondroitin sulfates from the vascular and lymphatic circulations. The internalized glycosaminoglycans are degraded in lysosomes, thus completing their normal turnover process. Sinusoidal endothelial cells of human liver, lymph node, and spleen express two HARE isoforms of 315 and 190 kDa. Here we report that the 190- and 315-kDa HARE isoforms, expressed stably either in Flp-In 293 cell lines or as soluble ectodomains, specifically bind heparin (Hep). The K(d) for Hep binding to purified 190- and 315-kDa HARE ectodomains was 17.2 +/- 4.9 and 23.4 +/- 5.3 nm, respectively. Cells expressing HARE readily and specifically internalized (125)I-streptavidin-biotin-Hep complexes, which was inhibited >70% by hyperosmolar conditions, confirming that uptake is mediated by the clathrin-coated pit pathway. Internalization of Hep occurred for many hours with an estimated HARE recycling time of approximately 12 min. Internalized fluorescent streptavidin-biotin-Hep was present in a typical endocytic vesicular pattern and was delivered to lysosomes. We conclude that HARE in the sinusoidal endothelial cells of lymph nodes and liver likely mediates the efficient systemic clearance of Hep and many different Hep-binding protein complexes from the lymphatic and vascular circulations.

Expression, processing, and glycosaminoglycan binding activity of the recombinant human 315-kDa hyaluronic acid receptor for endocytosis (HARE)

The hyaluronic acid (HA) receptor for endocytosis (HARE; also designated stabilin-2 and FEEL-2) mediates systemic clearance of glycosaminoglycans from the circulatory and lymphatic systems via coated pit-mediated uptake. HARE is primarily found as two isoforms (315- and 190-kDa) in sinusoidal endothelial cells of the liver, lymph node, and spleen. Here we characterize the ligand specificity and function of the large stably expressed 315-HARE isoform in Flp-In 293 cell lines. Like human spleen sinusoidal endothelial cells, Flp-In 293 cell lines transfected with a single cDNA encoding the full-length 315-HARE express both the 315-kDa and the proteolytically truncated 190-kDa isoforms in a ratio of approximately 3-4:1. The 190-kDa HARE isoform generated from the 315-kDa HARE and the 315-kDa HARE specifically bound 125I-HA. Like the 190-kDa HARE expressed alone (Harris, E. N., Weigel, J. A., and Weigel, P. H. (2004) J. Biol. Chem. 279, 36201-36209), the 190- and 315-kDa HARE isoforms expressed in 315-HARE cell lines were recognized by anti-HARE monoclonal antibodies 30, 154, and 159. All 315-HARE cell lines could endocytose and degrade 125I-HA. Competition studies with live cells indicate that 190-HARE and 315-HARE bind HA with higher apparent affinity (Kd approximately 10-20 nM) than chondroitin sulfate (CS) types A, C, D, or E. Only slight competition of HA endocytosis was observed with CS-B (dermatan sulfate) and chondroitin. Direct binding assays with the 315-HARE ectodomain revealed high affinity HA binding, and lower binding affinities for CS-C, CS-D, and CS-E. A majority of each HARE isoform was intracellular, within the endocytic system, suggesting transient surface residency typical of an active endocytic recycling receptor.

Hyaluronan and its receptors in mucoepidermoid carcinoma

BACKGROUND

Hyaluronan (HA) is a prominent extracellular matrix component undergoing continuous production and degradation. Increased HA levels have been described in a variety of tumors. The objective of this study was to examine the staining patterns of HA and two of its associated receptors (CD44 and HARE) in relation to the metastatic potential of mucoepidermoid carcinoma (MC). Immunohistochemical staining of preserved surgical specimens was used.

METHODS

Tissues from 12 patients with a histologic diagnosis of salivary MC (10 parotid, one submandibular gland, one minor salivary gland) were studied. Half (six of 12) of the patients had regional metastases. Tumor, normal salivary tissue, and regional lymph nodes were stained for HA, CD44, and HARE expression. Specimens were graded for staining intensity and a percent of the specimen stained.

RESULTS

Normal salivary tissue did not demonstrate epithelial cell surface HA expression, whereas HA was expressed on tumor cells and in regional lymph nodes containing metastases. These differences were both significant using Student's t test (p < .00002, and p < .0022, respectively). Tumors with positive nodes tended to have greater cell surface HA. Decreased expression or downregulation of HARE was also noted in involved lymph nodes. No differences in CD44 expression were seen between primary specimens and lymph nodes. The observed staining patterns for CD44 and HARE were not reflective of the metastatic potential of the primary MC.

CONCLUSIONS

Increased HA expression was seen on mucoepidermoid carcinoma cells compared with adjacent normal salivary gland epithelium. This observation may assist in explaining the development of regional metastasis in these tumors. We did not identify specific HA, CD44, or HARE staining patterns in primary lesions that were predictive of regional metastases.

Endocytic function, glycosaminoglycan specificity, and antibody sensitivity of the recombinant human 190-kDa hyaluronan receptor for endocytosis (HARE)

The human hyaluronan receptor for endocytosis (hHARE) mediates the endocytic clearance of hyaluronan (HA) and chondroitin sulfate from lymph fluid and blood. Two hHARE isoforms (190 and 315 kDa) are present in sinusoidal endothelial cells of liver, spleen, and lymph nodes (Zhou, B., McGary, C. T., Weigel, J. A., Saxena, A., and Weigel, P. H. (2003) Glycobiology 13, 339-349). Here we report the specificity and function of the 190-kDa HARE, expressed without the larger isoform, in Flp-In 293 cell lines (190hHARE cells). Like the native protein, recombinant hHARE contains approximately 25 kDa of N-linked oligosaccharides, binds HA in a ligand blot assay, cross-reacts with three anti-rat HARE monoclonal antibodies, and is inactivated by reduction. The 190hHARE cell lines mediated rapid, continuous (125)I-HA endocytosis and degradation for >1 day. About 30-50% of the total cellular receptors were on the cell surface, and their recycling time for reutilization was approximately 8.5 min. The average K(d) for the binding of HA to the 190-kDa hHARE at 4 degrees C was 7 nm with 118,000 total HA binding sites per cell. Competition studies at 37 degrees C indicated that the 190-kDa hHARE binds HA and chondroitin better than dermatan sulfate and chondroitin sulfates A, C, D, and E, but it does not bind to heparin, heparan sulfate, or keratan sulfate. Although competition was observed at 37 degrees C, none of the glycosaminoglycans tested, except HA, competed for (125)I-HA binding by 190hHARE cells at 4 degrees C. Anti-HARE monoclonal antibodies #30 and #154, which do not inhibit (125)I-HA uptake mediated by the 175-kDa rat HARE, partially blocked HA endocytosis by the 190-kDa hHARE. We conclude that the 190-kDa hHARE can function independently of other hHARE isoforms to mediate the endocytosis of multiple glycosaminoglycans. Furthermore, the rat and human small HARE isoforms have different glycosaminoglycan specificities and sensitivities to inhibition by cross-reacting antibodies.

Characterization of the recombinant rat 175-kDa hyaluronan receptor for endocytosis (HARE)

Hyaluronan (HA) and chondroitin sulfate (CS) clearance from lymph and blood in mammals is mediated by the HA receptor for endocytosis (HARE), which is present as two isoforms in rat and human (175/300 kDa and 190/315 kDa, respectively) in the sinusoidal endothelial cells of liver, spleen, and lymph nodes (Zhou, B., McGary, C. T., Weigel, J. A., Saxena, A., and Weigel, P. H. (2003) Glycobiology 13, 339-349). The small rat and human HARE proteins are not encoded directly by mRNA but are derived from larger precursors. Here we characterize the specificity and function of the 175-kDa HARE, expressed in the absence of the 300-kDa species, in stably transfected SK-Hep-1 cells. The HARE cDNA was fused with a leader sequence to allow correct orientation of the membrane protein. The recombinant rHARE contained approximately 25 kDa of N-linked oligosaccharides and, like the native protein, was able to bind HA in a ligand blot assay, even after de-N-glycosylation. SK-HARE cell lines demonstrated specific 125I-HA endocytosis, receptor recycling, and delivery of HA to lysosomes for degradation. The Kd for the binding of HA (number-average molecular mass approximately 133 kDa) to the 175-kDa HARE at 4 degrees C was 4.1 nm with 160,000 to 220,000 HA-binding sites per cell. The 175-kDa rHARE binds HA, dermatan sulfate, and chondroitin sulfates A, C, D, and E, but not chondroitin, heparin, heparan sulfate, or keratan sulfate. Surprisingly, recognition of glycosaminoglycans (GAGs) other than HA by native or recombinant HARE was temperature-dependent. Although competition was observed at 37 degrees C, none of the other GAGs competed for 125I-HA binding to SK-HARE cells at 4 degrees C. Anti-HARE monoclonal antibody-174 showed a similar temperature-dependence in its ability to block HA endocytosis. These data suggest that temperature-induced conformational changes may alter the GAG specificity of HARE. The results confirm that the 175-kDa rHARE does not require the larger HARE isoform to mediate endocytosis of multiple GAGs.

Purification and molecular identification of the human hyaluronan receptor for endocytosis

The clearance of hyaluronan (HA) and chondroitin sulfates from the circulating blood and lymph in the body is mediated by the membrane-bound HA receptor for endocytosis (HARE). Previously, we found that two HARE species of approximately 175 kDa and approximately 300 kDa are abundant in the sinusoidal endothelial cells in rat liver, spleen, and lymph nodes (Zhou et al. [2000], J. Biol. Chem., 275, 37733-37741). In the present study, immunocytochemical analysis of human tissues showed a similar pattern with abundant expression of HARE in the sinusoidal endothelial cells of human liver, spleen, and lymph nodes. The two human HARE proteins were immunoaffinity-purified from human spleen. Each protein was recognized in western blots using several anti-rat HARE monoclonal antibodies and was able to bind 125I-HA specifically. In nonreducing SDS-PAGE, these two human HARE species migrated at approximately 190 kDa and approximately 315 kDa; both proteins are approximately 15 kDa larger than the corresponding rat HAREs, although the de-N-glycosylated core proteins are essentially the same mass. After reduction, the human 190-kDa HARE gave a single 196-kDa species, which was not seen in the approximately 315-kDa HARE after reduction. The reduced approximately 315-kDa HARE yielded two major proteins at approximately 250 kDa and approximately 220 kDa. We determined the sequence of the human 190-kDa HARE cDNA based on analysis of internal tryptic peptides, as well as RT-PCR and 5' RACE analyses using human spleen and lymph node cDNA libraries. The human gene that encodes HARE is on chromosome 12.

A blocking antibody to the hyaluronan receptor for endocytosis (HARE) inhibits hyaluronan clearance by perfused liver

Hyaluronan (HA) and chondroitin sulfate clearance from lymph and blood is mediated by the hyaluronan receptor for endocytosis (HARE). The purification and molecular cloning (Zhou, B., Weigel, J. A., Saxena, A., and Weigel, P. H. (2002) Mol. Biol. Cell 13, 2853-2868) of this cell surface receptor were finally achieved after we developed monoclonal antibodies (mAbs) against HARE. There are actually two independent isoreceptors for HA, which in rat are designated the 175-kDa HARE and 300-kDa HARE. Only one mAb (number 174) effectively and completely blocked the specific uptake of 125I-HA at 37 degrees C by rat liver sinusoidal endothelial cells. 125I-HA binding to both the 175-kDa and 300-kDa HARE proteins in a ligand blot assay was almost completely inhibited by <1 microg/ml mAb-174, whereas mouse IgG had little or no effect. MAb-174 also performed very well in Western analysis, indirect fluorescence microscopy, and a variety of immuno-procedures. Immunohistochemistry using mAb-174 localized HARE to the sinusoidal cells of rat liver, spleen, and lymph node. Western analysis using mAb-174 revealed that the sizes of both HARE glycoproteins were the same in these three tissues. 125I-HA was taken up and degraded by excised rat livers that were continuously perfused ex vivo with a recirculating medium. This HA clearance and metabolism by liver, which is a physiological function of HARE, was very effectively blocked by mAb-174 but not by mouse IgG. The results indicate that mAb-174 will be a useful tool to study the functions of HARE and the physiological significance of HA clearance.

Use of Iodinated Hyaluronan Derivatives to Study Hyaluronan Binding, Endocytosis, and Metabolism by Cultured Cells

We have described several simple procedures to determine whether cells have specific receptors or binding proteins for HA. The advantage of using the uniquely modified 125I-labeled HA as a probe is that low levels of binding can be detected. It has been straightforward and productive to use 125I-labeled HA to quantitate cell surface and intracellular binding sites to determine affinity constants for HA binding and to determine whether the cell type being studied can efficiently endocytose and degrade the HA. The 125I-labeled HA preparations and assays described here and in Chapter 26 provide a very useful array of methods for studying the biochemistry and cell biology of HA.

Study of Hyaluronan-Binding Proteins and Receptors Using Iodinated Hyaluronan Derivatives

This chapter detailed methodology for the purification of high molecular weight HA, as well as procedures to fragment the HA to prepare large oligosaccharides in the range of 40,000-80,000 Da. The aforementioned procedures used to prepare HA-alkylamine and HA-Bolton-Hunter adducts, as well as 125I-labeled HA, have been very reproducible, and the latter preparations are of adequate length to retain high-affinity interactions and specific binding, e.g., to human fibrinogen and HARE. For example, we were able to isolate, characterize, and clone the rat HARE using 125I-labeled HA initially with the dot blot assay to monitor solubilization and partial purification, and later with the ligand blot assay, to identify the protein after SDS-PAGE. The ligand blot assay enabled us to determine that HARE is actually present as two discrete isoreceptors of different molecular masses. These techniques should provide a means to analyze purification strategies and to characterize additional HA receptors and binding proteins involved in a variety of physiologic processes.

Nonpalmitoylated human asialoglycoprotein receptors recycle constitutively but are defective in coated pit-mediated endocytosis, dissociation, and delivery of ligand to lysosomes

The hepatic asialoglycoprotein receptor (ASGP-R) internalizes desialylated glycoproteins via the clathrin-coated pit pathway and mediates their delivery to lysosomes for degradation. The human ASGP-R contains two subunits, H1 and H2. Cytoplasmic residues Cys(36) in H1, as well as Cys(54) and Cys(58) in H2 are palmitoylated (Zeng, F.-Y., and Weigel, P. H. (1996) J. Biol. Chem. 271, 32454). In order to study the function(s) of ASGP-R palmitoylation, we mutated these Cys residues to Ser and generated stably transfected SK-Hep-1 cell lines expressing either wild-type or nonpalmitoylated ASGP-Rs. Compared with wild-type ASGP-Rs, palmitoylation-defective ASGP-Rs showed normal ligand binding, intracellular distribution and trafficking patterns, and pH-induced dissociation profiles in vitro. However, continuous ASOR uptake, and the uptake of prebound cell surface ASOR were slower in cells expressing palmitoylation-defective ASGP-Rs than in cells expressing wild-type ASGP-Rs. Unlike native ASGP-Rs in hepatocytes or hepatoma cells, which mediate endocytosis via the clathrin-coated pit pathway and are almost completely inhibited by hypertonic medium, only approximately 40% of the ASOR uptake in SK-Hep-1 cells expressing wild-type ASGP-Rs was inhibited by hyperosmolarity. This result suggests the existence of an alternate nonclathrin-mediated internalization pathway, such as transcytosis, for the entry of ASGP-R.ASOR complexes into these cells. In contrast, ASOR uptake mediated by cells expressing palmitoylation-defective ASGP-Rs showed only a marginal difference under hypertonic conditions, indicating that most of the nonpalmitoylated ASGP-Rs were not internalized and processed normally through the clathrin-coated pit pathway. Furthermore, cells expressing wild-type ASGP-Rs were able to degrade the internalized ASOR, whereas ASOR dissociation was impaired and degradation was barely detectable in cells expressing nonpalmitoylated ASGP-Rs. We conclude that palmitoylation of the ASGP-R is required for its efficient endocytosis of ligand by the clathrin-dependent endocytic pathway and, in particular, for the proper dissociation and delivery of ligand to lysosomes.

Palmitoylation-defective asialoglycoprotein receptors are normal in their cellular distribution and ability to bind ligand, but are defective in ligand uptake and degradation

The hepatic asialoglycoprotein receptor (ASGP-R) is an endocytic recycling receptor that mediates the endocytosis of desialylated glycoproteins. The human ASGP-R is composed of two homologous subunits, H1 and H2, and the cytoplasmic Cys residues in both subunits are palmitoylated. To study the effects of palmitoylation on ASGP-R activity and function, we generated four types of stably transfected cell lines in SK-Hep-1 hepatoma cells, expressing wild-type, or partially or completely palmitoylation-defective ASGP-Rs containing Cys-to-Ser mutations in either one or both subunits. Scatchard analysis showed that all four stable cell lines expressed a similar number of binding sites for asialo-orosomucoid, with comparable dissociation constants of approximately 1-3nM. Immunofluorescence confocal microscopy indicated a normal distribution of the palmitoylation-defective H1 and H2 subunits compared to the wild-type. However, cell lines expressing palmitoylation-defective ASGP-Rs had markedly reduced rates of ligand uptake and degradation compared to cells expressing wild-type ASGP-Rs. We conclude that failure to palmitoylate Cys residues in either or both subunits of human ASGP-Rs results in very inefficient uptake and degradation of ligands.

Molecular cloning and functional expression of the rat 175-kDa hyaluronan receptor for endocytosis

We recently purified the rat liver hyaluronan receptor for endocytosis (HARE) and found abundant expression of 175- and approximately 300-kDa HARE species in sinusoidal endothelial cells of the liver, spleen, and lymph nodes. We report herein the first cloning and functional expression of the rat 175-kDa HARE. Peptide sequences were obtained from the purified 175-kDa HARE, and degenerate oligonucleotide primers were designed for reverse transcription-polymerase chain reaction and cDNA cloning. Results of 5'-rapid amplification of cDNA ends, Northern analysis, N-terminal sequence, and antibody reactivity analyses indicated the absence of mRNA directly encoding the 175-kDa HARE. This protein is most likely derived from a larger precursor. Accordingly, we constructed an artificial 4.7-kb cDNA encoding the 1431 amino acid 175-kDa HARE. The predicted type I membrane protein has a mass of 156,393 Da and a pI of 7.86. The 175-kDa HARE cDNA, fused to the N-terminal leader sequence of the Ig kappa-chain, was transfected transiently into COS-7 cells and stably into SK-Hep-1 cells, respectively, to assess hyaluronan or hyaluronic acid (HA)-binding activity and endocytosis. In both cases, HARE expression and HA-binding activity were detected. Furthermore, stable SK-175HARE cells demonstrated specific endocytosis of (125)I-HA and receptor recycling. Fluorescence-activated cell sorting analysis confirmed that recombinant HARE was expressed on the cell surface and that fluorescent HA uptake was inhibited by a specific blocking monoclonal antibody against HARE. Additionally, HARE was substantially colocalized with clathrin, but not with internalized HA that was delivered to lysosomes. The results confirm that recombinant 175-kDa HARE is an authentic endocytic receptor for HA and that this receptor can function independently of the approximately 300-kDa HARE. HARE is the first functionally identified member of a protein family that shares a similar organization of Fasciclin, epidermal growth factor-like, Xlink, and transmembrane domains.

The hyaluronan receptor for endocytosis (HARE) is not CD44 or CD54 (ICAM-1)

Mammalian liver contains an endocytic, recycling receptor that mediates the clearance of hyaluronan (HA) and chondroitin sulfate from the circulation. McCourt et al. [J. Biol. Chem. 269 (1994) 30081] previously reported that this endocytic liver HA receptor was ICAM-1. In contrast, we purified this HA receptor for endocytosis (HARE) from rat liver sinusoidal endothelial cells (LECs) and obtained two novel large proteins [Zhou et al., J. Biol. Chem. 274 (1999) 33831]. The goal of the present study was to clarify this inconsistency and determine whether CD44, which is also an HA receptor, or ICAM-1 (CD54) is identical to, or is part of, HARE. Although isolated liver LECs contain HARE, CD44, and ICAM-1, confocal fluorescence microscopy showed that the two latter proteins have cellular distributions that are distinct from and essentially nonoverlapping with HARE. HA accumulation by cultured LECs was inhibited >98% by an antibody against HARE and unaffected by antibodies to ICAM-1 or CD44, indicating that virtually all specific HA uptake is mediated by HARE and not by ICAM-1 or CD44. Finally, no reactivity was observed against purified HARE in an ELISA-based assay using CD44 or ICAM-1 antibodies. The results confirm that the mammalian endocytic HA receptor is HARE and is not ICAM-1 or CD44.

Endothelium in hepatic cavernous hemangiomas does not express the hyaluronan receptor for endocytosis

The liver contains two distinct endothelial cell types: vascular and sinusoidal. Although cavernous hemangioma is the most common benign tumor of the liver, vascular or sinusoidal endothelial cell differentiation has not been described. An endocytic receptor responsible for the uptake and degradation of hyaluronan is present in the sinusoidal endothelium of the liver. The hyaluronan receptor for endocytosis (HARE) may therefore be a useful marker for sinusoidal endothelial cell differentiation. Using monoclonal antibodies specific for HARE, CD31, and factor VIII, we completed an immunohistochemical study of the endothelial cells of both hepatic cavernous hemangiomas and of nonneoplastic human liver. The anti-HARE monoclonal antibodies showed diffuse strong staining of nonneoplastic liver sinusoidal endothelium. No staining of nonsinusoidal endothelium or the endothelial lining of the hemangiomas was seen with anti-HARE. In contrast, diffuse strong staining for factor VIII and CD31 was present in nonsinusoidal endothelium and cavernous hemangioma endothelium. Neither factor VIII nor CD31 staining was present in the sinusoidal endothelium. In conclusion, the endothelium of hepatic cavernous hemangiomas demonstrates vascular but not sinusoidal differentiation based on the absence of HARE and presence of CD31 and factor VIII.

Single-step formation of structurally defined bicyclic peptides via S(N)Ar cyclization

[structure: see text]. A solid-phase methodology for macrocyclization via an S(N)Ar reaction has been developed for the unambiguous formation of bicyclic peptidic compounds in a single cyclization step. The cyclization strategy involves the reaction of a 3,5-dihydroxybenzoyl group with two nitrofluorobenzoyl moieties. The symmetry of the dihydroxy aromatic ring results in a single product, and the remaining nitro groups are subsequently reduced to anilines and acylated.

Identification of the hyaluronan receptor for endocytosis (HARE)

Rat liver sinusoidal endothelial cells (LECs) express two hyaluronan (HA) receptors, of 175 and 300 kDa, responsible for the endocytic clearance of HA. We have characterized eight monoclonal antibodies (mAbs) raised against the 175-kDa HA receptor partially purified from rat LECs. These mAbs also cross-react with the 300-kDa HA receptor. The 175-kDa HA receptor is a single protein, whereas the 300-kDa species contains three subunits, alpha, beta, and gamma at 260, 230, and 97 kDa, respectively (Zhou, B., Oka, J. A., and Weigel, P. H. (1999) J. Biol. Chem. 274, 33831-33834). The 97-kDa subunit was not recognized by any of the mAbs in Western blots. Based on their cross-reactivity with these mAbs, the 175-, 230-, and 260-kDa proteins appear to be related. Two of the mAbs inhibit (125)I-HA binding and endocytosis by LECs at 37 degrees C. All of these results confirm that the mAbs recognize the bone fide LEC HA receptor. Indirect immunofluoresence shows high protein expression in liver sinusoids, the venous sinuses of the red pulp in spleen, and the medullary sinuses of lymph nodes. Because the tissue distribution for this endocytic HA receptor is not unique to liver, we propose the name HARE (HA receptor for endocytosis).

Initial treatment of ventricular fibrillation: defibrillation or drug therapy

The belief that defibrillation of unwitnessed ventricular fibrillation frequently results in asystole, combined with perceived low survival rates, led to deviation from "standard" advanced cardiac life support (ACLS) by physicians directing paramedics in the field. In nonstandard ACLS, intubation or drug therapy preceded defibrillation. This study retrospectively compared standard and nonstandard ACLS for ventricular fibrillation. The long-term survival rates were 12.3% (7/57) and 3.6% (6/168) for the two forms of ACLS, respectively (p = 0.03). The incidence of postcountershock asystole was 35% and 28% (p = 0.45). The survival rates for patients with a postcountershock rhythm and a pulse were 83% and 17% after standard and nonstandard ACLS (p less than 0.0001). Other factors reported to have a significant effect on survival were compared, and no significant differences (p greater than 0.05) were noted for mean age, sex, cardiopulmonary resuscitation (CPR) initiated by a bystander, ACLS response time, time to CPR, lay-witnessed arrest, or time to definitive care. The significant difference in the time to defibrillation (14 and 26 minutes) was expected. This is the first clinical study to clearly confirm the ACLS recommendation of early defibrillation before drug therapy in ventricular fibrillation.