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(The FASEB Journal. 2001;15:2454-2462.)
© 2001 FASEB

ß Amyloid peptide (Aß42) is internalized via the G-protein-coupled receptor FPRL1 and forms fibrillar aggregates in macrophages 1

HIROSHI YAZAWA*, ZU-XI YU{dagger}, TAKEDA{dagger}, YINGYING LE*, WANGHUA GONG{ddagger}, VICTOR J. FERRANS{dagger}, JOOST J. OPPENHEIM*, CHOU CHI H. LI{ddagger} and JI MING WANG*2

* Laboratory of Molecular Immunoregulation and
{ddagger} Intramural Research Support Program, SAIC Frederick, Center for Cancer Research, National Cancer Institute at Frederick, Maryland 21702, USA; and
{dagger} Pathology Section, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA

2Correspondence: LMI, CCR, NCI-Frederick, Building 560, Room 31–40, Frederick, MD 21702, USA. E-mail: wangji{at}mail.ncifcrf.gov


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The 42 amino acid form of ß amyloid (Aß42) plays a pivotal role in neurotoxicity and the activation of mononuclear phagocytes in Alzheimer’s disease (AD). Our recent study revealed that FPRL1, a G-protein-coupled receptor, mediates the chemotactic and activating effect of Aß42 on mononuclear phagocytes (monocytes and microglia), suggesting that FPRL1 may be involved in the proinflammatory responses in AD. We investigated the role of FPRL1 in cellular uptake and the subsequent fibrillar formation of Aß42 by using fluorescence confocal microscopy. We found that upon incubation with macrophages or HEK293 cells genetically engineered to express FPRL1, Aß42 associated with FPRL1 and the Aß42/FPRL1 complexes were rapidly internalized into the cytoplasmic compartment. The maximal internalization of Aß42/FPRL1 complexes occurred by 30 min after incubation. Removal of free Aß42 from culture supernatants at 30 min resulted in a progressive recycling of FPRL1 to the cell surface and degradation of the internalized Aß42. However, persistent exposure of the cells to Aß42 over 24 h resulted in retention of Aß42/FPRL1 complexes in the cytoplasmic compartment and the formation of Congo red positive fibrils in macrophages but not in HEK 293 cell transfected with FPRL1. These results suggest that besides mediating the proinflammatory activity of Aß42, FPRL1 is also involved in the internalization of Aß42, which culminates in the formation of fibrils only in macrophages.—Yazawa, H., Yu, Z.-X., Takeda, K., Le, Y., Gong, W., Ferrans, V. J., Oppenheim, J. J., Li, C. C. H., Wang, J. M. ß Amyloid peptide (Aß42) is internalized via the G-protein-coupled receptor FPRL1 and forms fibrillar aggregates in macrophages.


Key Words: amyloid ß • Alzheimer’s disease • internalization • colocalization


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Alzheimer’s disease (ad) is a progressive neurodegenerative disease characterized by the presence of senile plaques in the brain tissue (1) . Although the precise mechanisms of pathogenesis of AD remain undefined, it is well established that the 42 amino acid form of the ß amyloid peptide (Aß42) plays a central role in mediating neurotoxicity and the formation of senile plaques. Elevated level of Aß42, both in nonfibrillar (2 , 3) and fibrillar (4) forms, can be directly cytotoxic to neuronal cells; soluble nonfibrillar Aß42 in particular has been implicated for neuronal loss at the early stages of AD (reviewed in ref 5 ). Aß42 may activate mononuclear phagocytes in the brain and elicit inflammatory responses (6 7 8 9) . In fact, previous studies also suggest that the neurotoxicity of Aß42 may depend on the presence of mononuclear phagocytes (10) . There are two types of mononuclear phagocytes in the brain: perivascular macrophages and microglia; these are thought to be derived from circulating monocytic precursor cells that infiltrate the central nervous system during development as well as at various times postnatally (11 , 12) . Histological studies revealing activated microglia and perivascular macrophages closely associated with the dense cores in AD tissue support the hypothesis that these cells are actively involved in this disease. In vitro, Aß peptides are taken up by monocytes and microglia. They stimulate these cells to release proinflammatory cytokines and neurotoxic mediators (13 14 15) . This may account for the observations that anti-inflammatory drugs delay the onset of the AD dementia (6 7 8 9 , 16 , 17) , supporting the hypothesis that the pathogenesis and progress of AD involve a proinflammatory process in the brain.

Aß42 activates human mononuclear phagocytes typically through a receptor-mediated signaling pathway, prompting the search for cell surface receptors for Aß42. Scavenger receptor (SR) and receptor for advanced glycation end products (RAGE) have been proposed as putative receptors of Aß42 (18 19 20 21) . However, some studies failed to confirm the capacity of SR or RAGE to mediate the proinflammatory activity of Aß42 in mononuclear phagocytes. The presence of alternative Aß42 receptors on such cells has been postulated (22 23 24 25) . Recently, we found that a G-protein-coupled, seven-transmembrane receptor, FPRL1, mediates the migration and activation of monocytes and microglia induced by Aß42 (26 , 27) . Cells highly expressing the FPRL1 gene were detected in and around the senile plaques in the brain tissues of AD patients (20) . These cells were also stained positively for CD11b, a marker typical for mononuclear phagocytes in the brain. Thus, FPRL1 appears to be a relevant cell surface receptor that may account for the inflammatory responses elicited by Aß42. The present study aimed to define the effect of FPRL1 on Aß42 uptake by human mononuclear phagocytes. We report that after binding to FPRL1, Aß42 is rapidly internalized into the cytoplasmic compartment of the cells; with time, the internalized Aß42 forms fibrils only in macrophages.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Reagents and cells
W peptide (WKYMVm, W pep), a potent agonist for FPRL1 (28) , was custom-synthesized by the Department of Biochemistry, Colorado State University (Fort Collins, CO). Aß42 peptide (Aß42) was purchased from California Peptide Research (Napa, CA). Mouse monoclonal anti-human amyloid ß antibody was purchased from Sigma (St. Louis, MO). A rabbit polyclonal anti-FPRL1 antiserum was generated against a synthetic peptide derived from the carboxyl-terminal 20 amino acids of human FPRL1 conjugated to Keyhole limpet hemocyanin (C.-C. H. Li, unpublished observation). IgG was purified from the anti-FPRL1 serum by using Mab Trap G 2 kit from Amersham Pharmacia Biotech, Inc. (Piscataway, NJ). The purified antibody recognizes FPRL1 in macrophages and in HEK293 cells transfected with this receptor, but does not stain parental HEK293 cells or cells transfected with chemokine receptors. The preimmune serum does not react with FPRL1.

Human peripheral blood monocytes (PBM) were isolated from Buffy coats (Transfusion Medicine Department, NIH Clinical Center, Bethesda, MD) by using iso-osmotic Percoll gradient. The purity of cell preparations by morphology was > 90%. PBM were further differentiated to macrophages by culturing the cells in RPMI 1640 medium containing 0.1% bovine serum albumin, 0.01M HEPES (pH 7.4), and 20 ng/ml monocyte colony stimulating factor (MCSF, Pepro Tech, Rocky Hill, NJ). The cells were plated on 4-well chamber slides (Nalge Nunc International, Rochester, NY) at a density of 1 x 105 cells/well. HEK293 cells genetically engineered to express FPRL1 cDNA (FPRL1/293 cells) were kindly provided by Dr. P. M. Murphy (National Institute of Allergy and Infectious Diseases, NIH). FPRL1/293 cells were suspended in DMEM supplemented with 10% FBS (Hyclone, Logan, UT), 1 mM glutamine (Gibco-BRL, Grand Island, NY), and 800 µg/ml geneticin (G418, Gibco-BRL). The cells were also plated on 4-well chamber slides at a density of 2 x 105 cells/well.

Fluorescence confocal microscope
Human macrophages or FPRL1/293 cells grown on chamber slides were treated with FPRL1 agonists for different periods at 37°C. The cells were fixed in 4% paraformaldehyde for 10 min at room temperature. Slides were washed with PBS and incubated with 5% normal goat serum (Sigma) in PBS, 0.05% Tween-20 (PBS-T-NGS), for 1 h to block nonspecific binding sites and for permeabilization. The anti-Aß42 and anti-FPRL1 antibodies were applied and the slides were incubated for 1 h at room temperature. After three rinses with PBS, the slides were incubated with a mixture of FITC-conjugated goat anti-rabbit IgG and rhodamine-conjugated goat anti-mouse IgG (Sigma, 1:150 in TBS containing 3% BSA) for 30 min. The slides were mounted with an anti-fade, water-based mounting medium with 4,6-diamidino-2-phenylindole (DAPI; Vector Lab, Burlingame, CA) and analyzed under a laser scanning confocal fluorescence microscope (Leica TCS-4D DMIRBE, Heidelberg, Germany). Excitation wavelengths of 365 (for DAPI), 488 (for FITC), and 568 (for rhodamine) nm were used to generate fluorescence emission in blue, green, and red respectively. Colocalization of FPRL1 (green) and Aß42 (red) was reflected by yellow.

Congo red histochemistry
Cells on chamber slides were fixed with 4% paraformaldehyde and stained with hematoxylin for 2 min at room temperature. After 20 min incubation in a saturated NaCl solution containing 80% ethanol and 0.1% NaOH, the slides were reacted for 20 min with 0.2% Congo red. Destaining and dehydration were completed by washing the slides sequentially in 95% ethanol and 100% ethanol, followed by xylene. Coverslips were applied using Permount and the slides were viewed under light microscopy.

Detection of apoptosis
Apoptotic cells were detected by double labeling with annexin-V-FITC and propidium iodide (PI). Annexin-V binds to phosphatidylserine residues, which are translocated from the inner to the outer leaflet of the plasma membrane during the early stages of apoptosis (29 , 30) . Necrotic cells were distinguished from annexin-V-positive cells by counterstaining with PI (final concentration 1 µg/ml) (31 , 32) . Apoptotic cells were labeled by using an annexin-V kit according to manufacturer’s instructions (Santa Cruz Biotechnology, Santa Cruz, CA) and analyzed by flow cytometry.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Internalization of FPRL1 induced by the agonist W pep
In permeabilized FPRL1/293 cells, FPRL1 was detected with a polyclonal antibody and was distributed mostly on the cell membrane region, as shown by green fluorescence with confocal microscopy (Fig. 1 A). Therefore, we first studied the localization and trafficking of FPRL1 after incubation with W pep, which is derived from a random peptide library and is a highly potent chemotactic agonist for FPRL1 (28 , 33) . W pep dose-dependently induced a rapid internalization of FPRL1, which reached maximum after 15–30 min treatment at 37°C, with most of the green fluorescence localized in the cytoplasmic compartment of the FPRL1/293 cells (Fig. 1A, B ). When W pep was removed from culture medium after 30 min incubation with the cells, the green fluorescence progressively intensified on the membrane region; after 2 h, most of the fluorescence was located on the cell surface (Fig. 1C ). These results indicate that agonist-induced internalization of FPRL1 and receptor recycling after removal of the agonist can be detected by confocal microscopy.



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  		Figure 1. <381411161001>Figure 1 .

Detection of W pep-induced FPRL1 internalization. FPRL1/293 cells cultured on chamber slides were incubated at 37°C with different concentrations of W pep for various periods. The cells were washed, permeabilized, and stained with anti-FPRL1 antibody, followed by FITC-conjugated goat anti-rabbit IgG. The slides were viewed with confocal fluorescence microscope. FPRL1 was detected in green fluorescence and nuclei are shown as blue fluorescence (DAPI). A) FPRL1/293 cells were treated with different concentrations of W pep for 30 min. B) FPRL1/293 cells were treated with 1 µM W pep for different times (min). C) FPRL1/293 cells were treated with 1 µM W pep for 30 min, thoroughly washed, and then were examined for FPRL1 staining at different times (h).

Colocalization of Aß42 and FPRL1
As our recent study had revealed that Aß42 is a chemotactic agonist for FPRL1 (26 , 27) , we investigated the capacity of Aß42 to induce FPRL1 internalization. Incubation of FPRL1/293 cells and human macrophages for 30 min with Aß42 induced the internalization of FPRL1 in association with Aß42 into the cytoplasmic compartment in a dose-dependent manner (Fig. 2 A, B). Maximal internalization of Aß42 and FPRL1 complexes occurred when 10 µM or more Aß42 was used to stimulate the cells. Similar concentrations of Aß42 have been shown to induce potent chemotaxis and Ca2+ flux in mononuclear phagocytes (monocytes and microglia) and FPRL1/293 cells in our previous studies (26 , 27) . The concentrations of Aß42 used in our study were within or below those used by other laboratories to study the biological activities of the Aß42 (2 , 10 , 23 24 25) . Such concentrations of Aß42 have been detected in brain tissues of AD patients and mice transfected with human amyloid precursor protein gene (34 35 36 37) and are pathophysiologically relevant. In control experiments, neither Aß42 nor FPRL1 was detected in parental HEK293 cells even after treatment with 20 µM of Aß42 (Fig. 2C ). Investigation of the kinetics showed that at 5 min, Aß42 and FPRL1 were colocalized on the cell surface, followed by a rapid and progressive internalization of the Aß42/FPRL1 complex. As for W pep, the Aß42-induced FRPL1 internalization reached a maximal level at 15–30 min in FPRL1/293 cells (Fig. 3 A) and macrophages (Fig. 3B ). When FPRL1/293 cells or macrophages were further cultured in Aß42-free medium, the FPRL1 could be detected on the cell surface within 2 h (Fig. 4 A, B), suggesting rapid receptor recycling after depletion of Aß42 from culture supernatant. However, the antigenic Aß42 was detectable in the cytoplasmic region even 24 h after removal of Aß42 (Fig. 4) . These data suggest that a transient interaction of Aß42 with FPRL1 promotes internalization of the ligand/receptor complex and that Aß42 was released intracellularly before the receptor FPRL1 travels back to the cell surface.



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  		Figure 2. Internalization and colocalization of FPRL1/Aß42 complex. FPRL1/293 cells (A) and macrophages (B) cultured on chamber slides were incubated with various concentrations of Aß42 at 37°C for 30 min. The cells were rinsed, permeabilized, and stained with anti-FPRL1 antibody and a mouse anti-Aß42 antibody. The cells were further treated with FITC conjugated goat anti-rabbit IgG and rhodamine conjugated goat anti-mouse IgG, then examined under a confocal microscope. FPRL1 was detected in green fluorescence and Aß42 in red. Colocalization of FPRL1 and Aß42 was displayed by yellow fluorescence as a result of superimposing fluorescence images of FPRL1 (green) and Aß42 (red). As a control, parental HEK293 cells were incubated with 20 µM Aß42 at 37°C for 30 min, then examined for fluorescence with antibodies against Aß42 and FPRL1 (C).



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  		Figure 3. Time-dependent internalization of Aß42/FPRL1. FPRL1/293 cells (A) and macrophages (B) were treated with 10 µM Aß42 for different periods (min). FPRL1 (green), Aß42 (red) and the complexes (yellow) were examined with confocal microscope.



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  		Figure 4. Recycling of FPRL1 after Aß42 treatment. FPRL1/293 cells (A) and macrophages (B) were incubated with 10 µM Aß42 at 37°C for 30 min. The cells were thoroughly washed and further incubated in Aß42-free medium for various periods (h). Fluorescence of FPRL1 (green) and Aß42 (red) was visualized by confocal microscope after staining the cells with anti-FPRL1 and anti-Aß42 antibodies. Colocalization of FPRL1 and Aß42 was displayed by yellow fluorescence.

The effect of persistent exposure of FPRL1 to Aß42
Since a hallmark of AD is an aberrant and continual production and deposition of Aß42 in the brain, we investigated the effect of prolonged treatment of FPRL1/293 cells and macrophages with Aß42 on FPRL1 internalization and recycling. The persistent presence of Aß42 in culture supernatant for up to 48 h resulted in the retention of Aß42/FPRL1 complexes in the cytoplasmic region in FPRL1/293 cells and macrophages (Fig. 5 A, B), and no FPRL1 could be detected on the cell surface. A cytopathic effect was observed when macrophages or FPRL1/293 cells were exposed to Aß42 for 48 h as shown by increased proportion of apoptotic cells (Fig. 6 ). In contrast to Aß42, W pep treatment for 48 h did not increase the apoptosis of FPRL1/293 cells or macrophages. Aß42 did not induce any apoptosis of parental HEK293 cells. These results suggest that the apoptotic effect was specific for Aß42 through its interaction with FPRL1.



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  		Figure 5. Internalization of FPRL1 after persistent cell exposure to Aß42. FPRL1/293 cells (A) and macrophages (B) cultured on chamber slides were incubated with 10 µM Aß42 for various periods (h) at 37°C. Fluorescence of FPRL1 (green) and Aß42 (red) was visualized by confocal microscope after staining the cells with anti-FPRL1 and anti-Aß42 antibodies. Colocalization of FPRL1 and Aß42 was displayed by yellow.



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  		Figure 6. Aß42 induced apoptosis of FPRL1/293 cells and macrophages. Macrophages, FPRL1/293 cells, and parental HEK293 cells were cultured for 48 h with medium alone, 10 µM Aß42, or 1 µM W pep. After simultaneous staining with annexin-V-FITC and PI, cells were analyzed by flow cytometry. The upper right quadrant represents necrotic cells; the lower right quadrant represents apoptotic cells; the lower left quadrant represents viable, nonapoptotic cells. Numbers denote the cell percentage.

Formation of fibrils in macrophages exposed to Aß42
It is well known that Aß42 forms fibrillar aggregates both in vivo and in vitro, so we investigated the effect of Aß42/FPRL1 internalization on intracellular aggregation of Aß42. Macrophages incubated with Aß42 for 24 h were stained positively with Congo red; this staining was markedly intensified at 48 h (Fig. 7 ), suggesting that when Aß42 is internalized with FPRL1 in macrophages, it has the potential to become aggregated. Although massive colocalization of Aß42/FPRL1 could be observed at 24 h and 48 h in FPRL/293 cells, we failed to detect Congo red positive fibrils in these cells (Fig. 7) . These results indicate that Aß42 internalized into FPRL1 transfected cells do not undergo intracellular fibrillar formation as in macrophages. However, these cells exhibited a greater tendency than macrophages to undergo apoptotic death after exposure to Aß42 (Fig. 6) . In contrast to Aß42, W pep did not form Congo red positive fibrils in macrophages after 48 h incubation (Fig. 7) , suggesting that even though Aß42 and W peptide are both agonists for FPRL1, they exhibited very different physicochemical properties.



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  		Figure 7. Congo red staining of macrophages and FPRL1/293 cells after exposure to Aß42. Macrophages (upper panel) and FPRL1/293 cells (lower panel) were incubated with 10 µM Aß42 and 1 µM W pep for various periods at 37°C on chamber slides. The cells were thoroughly washed, fixed, and stained with Congo red. The cells were counterstained by hematoxylin.

Effect of colchicine on Aß42/FPRL1 internalization
Having established that Aß42 associated with FPRL1 could be rapidly internalized and the internalized Aß42 form fibrils in macrophages, we asked whether anti-inflammatory agents might interfere with the interaction between Aß42 and FPRL1 and the subsequent ligand/receptor internalization. We used colchicine, an antimitotic agent that has been reported to inhibit the function of microtubules (38) and to abolish Aß42-induced monocyte release of neurotoxic mediators (39 , 40) . We observed that colchicine was a potent inhibitor of Aß42-induced chemotaxis of both monocytes and FPRL1/293 cells (W. Gong et al., unpublished data). In macrophages and FPRL1/293 cells treated with colchicine, Aß42 still rapidly associated and could be colocalized with FPRL1 on the cell surface within 5 min (Fig. 8 A). However, the Aß42/FPRL1 complexes failed to internalize and remained on the cell surface even after 30 min incubation at 37°C (Fig. 8A ). These results suggest that whereas colchicine does not inhibit the cell surface expression of FPRL1 and its initial binding of Aß42, it interferes with FPRL1/Aß42 complex internalization and the resultant cell signaling (chemotaxis), presumably through inhibition of microtubule movement. Colchicine-treated macrophages were not significantly stained with Congo red after 48 h incubation with Aß42 (Fig. 8B ): only a brownish staining was visible, which could have been due to early stage of extracellular aggregation of Aß42. Thus, colchicine appears to be capable of preventing cell activation by Aß42 and the subsequent intracellular deposition of Aß42 fibrils in macrophages.



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  		Figure 8. The effect of colchicine on FPRL1 and Aß42 internalization and fibrillar formation. A) FPRL1/293 cells (left panel) and macrophages (right panel) were treated with colchicine (5 µg/ml) for 1 h before incubation with Aß42 (10 µM). After various periods of time (min), cells were prepared with anti-FPRL1 and anti-Aß42 antibodies for examination under fluorescence confocal microscope. FPRL1 was shown in green fluorescence and Aß42 in red. Colocalization of FPRL1 and Aß42 was displayed by yellow. B) FPRL1/293 cells (upper panel) and macrophages (lower panel) were pretreated with colchicine (5 µg/ml) for 1 h before incubation with Aß42 (10 µM) for 48 h. Cells were then examined for fluorescence images of FPRL1 and Aß42 by confocal microscope. Cells treated in the same manner with colchicine and Aß42 were also examined by Congo red staining.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Amyloid ß peptides (especially the Aß42) play an important role in the progression of AD. Both soluble and fibrillar forms of Aß42 have been reported to be neurotoxic. It has been suggested that the soluble, nonfibrillar form may result in loss of neuronal cells in the early stages of AD possibly by interacting with certain ‘toxin receptor’ on the cell surface (2 3 4 5) . However, the nature of such a toxin receptor has not been defined. On the other hand, many observations suggest an indirect pathway that involves a proinflammatory process mediated by Aß42-activated microglial cells (7 8 9 10) , the brain counterpart of the mononuclear phagocytes (41 42 43) . In support of the proinflammatory theory, activated microglial cells migrate to form clusters in and around the senile plaques in AD brain, and both brain microglia or monocytes have been shown to release neurotoxic mediators in vitro in response to Aß peptides (42) . In transgenic mice overexpressing human Aß in the brain, CD11b positive mononuclear phagocytes have been detected in and around AD-like plaques (44) . Patients receiving anti-inflammatory drugs have been reported to show significantly delayed development of AD dementia, and such drugs inhibit Aß42-stimulated release of neurotoxins by mononuclear phagocytes in vitro (39 , 45) .

To identify the cellular receptor(s) that may mediate the effect of Aß42 on mononuclear phagocytes, we showed that the G-protein-coupled receptor FPRL1 was used by Aß42 to induce mononuclear phagocyte migration and activation in vitro (26 , 27) . Elevated FPRL1 gene expression was detected in CD11b-positive mononuclear phagocytes that infiltrate the plaques in brain tissues of the AD patients (26) . FPRL1 belongs to the superfamily of G-protein-coupled receptors that includes the receptors for chemoattractants and neurotransmitters. After ligand binding, it is a common feature for these receptors to undergo internalization, which may involve different pathways. The adrenergic (46) and thrombin (47) receptors are internalized by a classical endocytic pathway through clathrin-coated pits whereas, angiotensin 2 type 1A receptors are internalized through non-clathrin-coated vesicles (48) . Studies of FPR, a receptor that shows 69% identity at amino acid level to FPRL1 (49) , revealed that agonist-induced FPR internalization in HEK293 cells occurs in an arrestin-independent manner and is not mediated through clathrin-coated pits (50) . Whether FPRL1 internalization is also mediated by a pathway used by FPR requires further investigation. It is possible that due to the intrinsic differences in signaling effectors in native mononuclear phagocytes and HEK293 cells, which are of the epithelial origin, the mechanisms of internalization in these cell types could be divergent.

Because of a close association of monocytic phagocytes with the senile plaques in AD, the role of these cells in the plaque formation has been investigated. Microglial cells accumulate in greater numbers around amyloid-containing neuritic plaques than diffuse plaques in amyloid precursor protein transgenic mice (44) , suggesting that microglial cells may be involved in the conversion of nonfibrillar Aß42 into amyloid fibrils, a function that has been ascribed to peripheral macrophages in systemic amyloidosis. Several studies of the association of monocytic phagocytes with various stages of plaque formation in elderly and AD patients also implied a role for these cells in transforming diffuse plaques into neuritic plaques (51 , 52) . Ultrastructural evidence suggests that mononuclear phagocytes may have the capacity to lay down amyloid fibrils within plaques (53) . Our present study showed that after prolonged culture, Aß42 internalized through the receptor FPRL1 forms Congo red positive fibrils in macrophages but not in HEK293 cells transfected with FPRL1. Thus, macrophages (but not epithelial cells) may indeed provide a microenvironment that fosters intracellular deposition of Aß42 if the cells are subjected to prolonged exposure to Aß42. Although Aß42 internalized in HEK293 cells transfected with FPRL1 do not form fibrils, these cells showed a greater tendency to apoptotic death (Fig. 6) , suggesting that Aß42 could be directly cytotoxic to nonleukocytic cells as long as they express FPRL1. However, it is not clear whether neuronal cells express FPRL1 to mediate the cytotoxic effect of Aß42. In our preliminary experiments, we found that a human neuroblastoma cell line, which has been reported to be susceptible to the cytotoxicity of Aß42, expressed the mRNA for FPRL1 (Y. Le et al., unpublished observation). Whether normal neurons also express functional FPRL1 is under investigation.

Although the intracellular microenvironment in monocytic phagocytes may promote fibrillar formation of the internalized Aß42, the uptake of Aß42 by these cells may also serve to maintain a dynamic balance between amyloid deposition and removal, a process that determines the amyloid burden in AD brain (53) . Cultured rodent microglial cells and human monocytes have been shown to internalize Aß42 peptides, and the smaller Aß42 aggregates were more efficiently internalized than the fibrillar forms of Aß42 (54 55 56) . Aß42 incubated with rat microglial cells was taken up and could be degraded (57 , 58) . These cells were also capable of breaking apart phagocytosed plaque cores (57) . The capacity of mononuclear phagocytes to remove amyloid deposits was further shown by a recent observation of Aß42 colocalization with a microglial activation marker, MHC2, in Aß42-immunized PDAPP transgenic mice in which amyloid deposits were largely cleared (58) . In PDAPP transgenic mice, the AD-like lesions in the brain were of the diffused type, which is not associated with as prominent a proinflammatory response as seen in the dense core type lesions (58) . Thus, the capacity of the host cells (particularly mononuclear phagocytes) to take up and clear Aß42 may be determined by the levels of Aß42 produced and the duration of cell exposure. This concept is supported by our observation that removal of Aß42 from culture supernatants of macrophages after 30 min incubation resulted in a rapid recycling of the FPRL1 to the cell surface. Although Aß42 could be detected intracellularly after 24 h, the cells were not stained by Congo red and the Aß42 was no longer detectable after 48 h, suggesting that the lower levels of Aß42 had been degraded.

Although uptake of Aß42 by mononuclear phagocytes may represent a host defense in response to pathogenic agents and was generally considered beneficial, Aß42 interaction with FPRL1 and the resultant internalization are clearly associated with a proinflammatory response such as cell migration and activation (26 , 27) . It has been shown that brain microglia and peripheral mononuclear phagocytes stimulated with Aß42 can release neurodestructive reactive oxygen species (13 , 27) , reactive nitrogen and tumor necrosis factor {alpha} (14 , 15) , all of which were elevated in AD brain. Several retrospective and prospective epidemiologic studies have shown beneficial effects of nonsteroidal anti-inflammatory drugs in delaying the onset of AD dementia (reviewed in refs 6 , 7 , 9 ). Such agents, including colchicine, have been shown to inhibit production of neurotoxic mediators by mononuclear phagocytes (39) . Our present study with colchicine demonstrated its ability to block FPRL1-mediated Aß42 internalization in both native mononuclear phagocytes and FPRL1/293 cells. The FPRL1-mediated cell migration in response to Aß42 was also inhibited (W. Gong, unpublished observation). These observations provide considerable evidence that the beneficial effects of anti-inflammatory agents on AD dementia may be due to their interference with Aß42 elicited inflammatory process mediated by FPRL1 on mononuclear phagocytes. Research is under way to further delineate the role of FPRL1 in AD and its potential as a therapeutic target.


   ACKNOWLEDGMENTS
 
The authors thank P. M. Murphy and J. L. Gao for providing FPRL1/293 cells, N. Dunlop for technical support, and C. Fogle and C. Nolan for secretarial assistance.


   FOOTNOTES
 
1 The content of this publication does not necessarily reflect the views or policies check of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. government. The publisher or recipient acknowledges right of the U.S. government to retain a nonexclusive, royalty-free license in and to any copyright covering the article. This project has been funded in whole or in part with federal funds from the National Cancer Institute, National Institutes of Health, under contract no. NO1-CO-56000. This project has been funded in whole or in part with federal funds from the National Cancer Institute, National Institutes of Health, under contract no. NO1-CO-56000.

Received for publication April 11, 2001. Revision received July 18, 2001.
   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Selkoe, D. J. (1999) Translating cell biology into therapeutic advances in Alzheimer’s disease.. Nature (London) 399(Suppl.),A23-A31[Medline]
  2. Hartley, D. M., Walsh, D. M., Ye, C. P., Diehl, T., Vasquez, S., Vassilev, P. M., Teplow, D. B., Selkoe, D. J. (1999) Protofibrillar intermediates of amyloid beta-protein induce acute electrophysiological changes and progressive neurotoxicity in cortical neurons. J. Neurosci. 19,8876-8884[Abstract/Free Full Text]
  3. Lambert, M. P., Barlow, A. K., Chromy, B. A., Edwards, C., Freed, R., Liosatos, M., Morgan, T. E., Rozovsky, I., Trommer, B., Viola, K. L., Wals, P., Zhang, C., Finch, C. E., Krafft, G. A., Klein, W. L. (1998) Diffusible, nonfibrillar ligands derived from Abeta1–42 are potent central nervous system neurotoxins. Proc. Natl. Acad. Sci. USA 95,6448-6645[Abstract/Free Full Text]
  4. Lorenzo, A., Yankner, B. A. (1994) Beta-amyloid neurotoxicity requires fibril formation and is inhibited by congo red. Proc. Natl. Acad. Sci. USA 91,12243-12247[Abstract/Free Full Text]
  5. Klein, W. L., Krafft, G. A., Finch, C. E. (2001) Targeting small Abeta oligomers: the solution to an Alzheimer’s disease conundrum?. Trends Neurosci 24,219-224[Medline]
  6. Pachter, J. S. (1997) Inflammatory mechanisms in Alzheimer disease: the role of beta amyloid/glial interactions. Mol. Psychiatry 2,91-95[Medline]
  7. McGeer, P. L., McGeer, E. G. (1999) Inflammation of the brain in Alzheimer’s disease: implications for therapy. J. Leukoc. Biol. 65,409-415[Abstract]
  8. Kalaria, R. N. (1999) Microglia and Alzheimer’s disease. Curr. Opin. Hematol. 6,15-24[Medline]
  9. . Neuroinflammatory Working Group (2000) Inflammation and Alzheimer’s disease. Neurobiol. Aging 21,383-342[Medline]
  10. London, J. A., Biegel, D., Pachter, J. S. (1996) Neurocytopathic effects of beta-amyloid-stimulated monocytes: a potential mechanism for central nervous system damage in Alzheimer disease. Proc. Natl. Acad. Sci. USA 93,4147-4152[Abstract/Free Full Text]
  11. Hickey, W. F., Kimura, H. (1998) Perivascular microglial cells of the CNS are bone marrow-derived and present antigen in vivo. Science 239,290-292
  12. Ling, E. A., Wong, W. C. (1993) The origin and nature of ramified and amoeboid microglia: a historical review and current concepts. Glia 7,9-18[Medline]
  13. Colton, C. A., Gilbert, D. L. (1987) Production of superoxide anions by a CNS macrophage, the microglia. FEBS Lett 223,284-288[Medline]
  14. Chao, C. C., Hu, S., Molitor, T. W., Shaskan, E. G., Peterson, P. K. (1992) Activated microglia mediate neuronal cell injury via a nitric oxide mechanism. J. Immunol. 149,2736-2741[Abstract]
  15. van der Laan, L. J., Ruuls, S. R., Weber, K. S., Lodder, I. J., Dopp, E. A., Dijkstra, C. D. (1996) Macrophage phagocytosis of myelin in vitro determined by flow cytometry: phagocytosis is mediated by CR3 and induces production of tumor necrosis factor-alpha and nitric oxide. J. Neuroimmunol. 70,145-152[Medline]
  16. McGeer, P. L., Schulzer, M., McGeer, E. G. (1996) Arthritis and anti-inflammatory agents as possible protective factors for Alzheimer’s disease: a review of 17 epidemiologic studies. Neurology 47,425-432[Abstract/Free Full Text]
  17. Hull, M., Fiebich, B. L., Schumann, G., Lieb, K., Bauer, J. (1999) Anti-inflammatory substances—a new therapeutic option in Alzheimer’s disease. Drug Discov. Today 4,275-282[Medline]
  18. El Khoury, J., Hickman, S. E., Thomas, C. A., Cao, L., Silverstein, S. C., Loike, J. D. (1996) Scavenger receptor-mediated adhesion of microglia to beta-amyloid fibrils. Nature (London) 382,716-719[Medline]
  19. El Khoury, J., Hickman, S. E., Thomas, C. A., Loike, J. D., Silverstein, S. C. (1998) Microglia, scavenger receptors, and the pathogenesis of Alzheimer’s disease. Neurobiol. Aging 19,S81-S84[Medline]
  20. Paresce, D. M., Ghosh, R. N., Maxfield, F. R. (1996) Microglial cells internalize aggregates of the Alzheimer’s disease amyloid beta-protein via a scavenger receptor. Neuron 17,553-565[Medline]
  21. Yan, S. D., Chen, X., Fu, J., Chen, M., Zhu, H., Roher, A., Slattery, T., Zhao, L., Nagashima, M., Morser, J., Migheli, A., Nawroth, P., Stern, D., Schmidt, A. M. (1996) RAGE and amyloid-beta peptide neurotoxicity in Alzheimer’s disease. Nature (London) 382,685-691[Medline]
  22. Antic, A., Dzenko, K. A., Pachter, J. S. (2000) Engagement of the scavenger receptor is not responsible for beta-amyloid stimulation of monocytes to a neurocytopathic state. Exp. Neurol. 161,96-101[Medline]
  23. McDonald, D. R., Bamberger, M. E., Combs, C. K., Landreth, G. E. (1998) beta-Amyloid fibrils activate parallel mitogen-activated protein kinase pathways in microglia and THP1 monocytes. J. Neurosci. 18,4451-4460[Abstract/Free Full Text]
  24. Lorton, D., Schaller, J., Lala, A., De Nardin, E. (2000) Chemotactic-like receptors and Abeta peptide induced responses in Alzheimer’s Disease. Neurobiol. Aging 21,463-473[Medline]
  25. Combs, C. K., Johnson, D. E., Cannady, S. B., Lehman, T. M., Landreth, G. E. (1999) Identification of microglial signal transduction pathways mediating a neurotoxic response to amyloidogenic fragments of beta-amyloid and prion proteins. J. Neurosci. 19,928-939[Abstract/Free Full Text]
  26. Le, Y., Gong, W., Tiffany, H. L., Tumanov, A., Nedospasov, S., Shen, Weiping., Dunlop, N. M., Gao, J. L., Murphy, P. M., Oppenheim, J. J., Wang, J. M. (2001) Amyloid ß42 activates a G-protein-coupled chemoattractant receptor. FPR-like-1. J. Neurosci. 21,RC123
  27. Tiffany, H. L., Lavigne, M. C., Cui, Y. H., Wang, J. M., Leto, T. L., Gao, J. L., Murphy, P. M. (2001) Amyloid-beta induces chemotaxis and oxidant stress by acting at formylpeptide receptor 2, a G protein-coupled receptor expressed in phagocytes and brain. J. Biol. Chem. 276,23645-23652[Abstract/Free Full Text]
  28. Le, Y., Gong, W., Li, B., Dunlop, N. M., Shen, W., Su, S. B., Ye, R. D., Wang, J. M. (1999) Utilization of two seven-transmembrane, G protein-coupled receptors, formyl peptide receptor-like 1 and formyl peptide receptor, by the synthetic hexapeptide WKYMVm for human phagocyte activation. J. Immunol. 163,6777-6784[Abstract/Free Full Text]
  29. Koopman, G., Reutelingsperger, C. P. M., Kuijten, G. A. M., Keehnen, R. M. J., Pals, S. T., Van Oers, M. H. J (1994) Annexin-V for flow-cytometric detection of phosphatidylserine expression on B-cells undergoing apoptosis. Blood 84,1415-1420[Abstract/Free Full Text]
  30. Martin, S. J., Reutelingsperger, C. P., McGahon, A. J., Rader, J. A., van Schie, R. C., LaFace, D. M., Green, D. R. (1995) Early redistribution of plasma membrane phosphatidylserine is a general feature of apoptosis regardless of the initiating stimulus: inhibition by overexpression of Bcl-2 and Abl. J. Exp. Med. 182,1545-1556[Abstract/Free Full Text]
  31. Heidenreich, S., Schmidt, M., August, C., Cullen, P., Rademaekers, A., Pauels, H. G. (1997) Regulation of human monocyte apoptosis by the CD14 molecule. J. Immunol. 159,3178-3188[Abstract]
  32. Mangan, D. F., Welch, G. R., Wahl, S. M. (1991) Lipopolysaccharide, tumor necrosis factor-alpha, and IL-1 beta prevent programmed cell death (apoptosis) in human peripheral blood monocytes. J. Immunol. 146,1541-1546[Abstract]
  33. Seo, J. K., Bae, Y. S., Song, H., Baek, S. H., Kim, B. S., Choi, W. S., Suh, P. G., Ryu, S. H. (1998) Distribution of the receptor for a novel peptide stimulating phosphoinositide hydrolysis in human leukocytes. Clin. Biochem. 31,137-141[Medline]
  34. Kuo, Y. M., Emmerling, M. R., Lampert, H. C., Hempelman, S. R., Kokjohn, T. A., Woods, A. S., Cotter, R. J., Roher, A. E. (1999) High levels of circulating Abeta42 are sequestered by plasma proteins in Alzheimer’s disease. Biochem. Biophys. Res. Commun. 257,787-791[Medline]
  35. McLean, C. A., Cherny, R. A., Fraser, F. W., Fuller, S. J., Smith, M. J., Beyreuther, K., Bush, A. I., Masters, C. L. (1999) Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer’s disease. Ann. Neurol. 46,860-866[Medline]
  36. Kawarabayashi, T., Younkin, L. H., Saido, T. C., Shoji, M., Ashe, K. H., Younkin, S. G. (2001) Age-dependent changes in brain, CSF, and plasma amyloid (beta) protein in the Tg2576 transgenic mouse model of Alzheimer’s disease. J. Neurosci. 21,372-381[Abstract/Free Full Text]
  37. Funato, H., Yoshimura, M., Kusui, K., Tamaoka, A., Ishikawa, K., Ohkoshi, N., Namekata, K., Okeda, R., Ihara, Y. (1998) Quantitation of amyloid beta-protein (A beta) in the cortex during aging and in Alzheimer’s disease. Am. J. Pathol. 152,1633-1640[Abstract]
  38. Rossi, M., Gorbunoff, M. J., Caruso, F., Wing, B., Perez-Ramirez, B., Timasheff, S. N. (1996) Structural analysis of the substoichiometric and stoichiometric microtubule-inhibiting biphenyl analogues of colchicine. Biochemistry 35,3286-3289[Medline]
  39. Dzenko, K. A., Weltzien, R. B., Pachter, J. S. (1997) Suppression of A beta-induced monocyte neurotoxicity by antiinflammatory compounds. J. Neuroimmunol. 80,6-12[Medline]
  40. Heinzelmann, M., Platz, A., Flodgaard, H., Polk, H. C., Miller, F. N. (1999) Endocytosis of heparin-binding protein (CAP37) is essential for the enhancement of lipopolysaccharide-induced TNF-alpha production in human monocytes. J. Immunol. 162,4240-4245[Abstract/Free Full Text]
  41. Ford, A. L., Foulcher, E., Lemckert, F. A., Sedgwick, J. D. (1996) Microglia induce CD4 T lymphocyte final effector function and death. J. Exp. Med. 184,1737-1745[Abstract/Free Full Text]
  42. Meda, L., Baron, P., Prat, E., Scarpini, E., Scarlato, G., Cassatella, M. A., Rossi, F. (1999) Proinflammatory profile of cytokine production by human monocytes and murine microglia stimulated with beta-amyloid[25–35]. J. Neuroimmunol. 93,45-52[Medline]
  43. Yates, S. L., Burgess, L. H., Kocsis-Angle, J., Antal, J. M., Dority, M. D., Embury, P. B., Piotrkowski, A. M., Brunden, K. R. (2000) Amyloid beta and amylin fibrils induce increases in proinflammatory cytokine and chemokine production by THP-1 cells and murine microglia. J. Neurochem. 74,1017-1025[Medline]
  44. Stalder, M., Phinney, A., Probst, A., Sommer, B., Staufenbiel, M., Jucker, M. (1999) Association of microglia with amyloid plaques in brains of APP23 transgenic mice. Am. J. Pathol. 154,1673-1684[Abstract/Free Full Text]
  45. Breitner, J. C., Welsh, K. A., Helms, M. J., Gaskell, P. C., Gau, B. A., Roses, A. D., Pericak-Vance, M. A., Saunders, A. M. (1995) Onset of Alzheimer’s disease with nonsteroidal anti-inflammatory and histamine H2 blocking drugs. Aging 16,523-530
  46. von Zastrow, M., Kobilka, B. K. (1992) Ligand-regulated internalization and recycling of human beta 2-adrenergic receptors between the plasma membrane and endosomes containing transferrin receptors. J. Biol. Chem. 267,3530-3538[Abstract/Free Full Text]
  47. Hoxie, J. A., Ahuja, M., Belmonte, E., Pizarro, S., Parton, R., Brass, L. F. (1993) Internalization and recycling of activated thrombin receptors. J. Biol. Chem. 268,13756-13763[Abstract/Free Full Text]
  48. Zhang, J., Ferguson, S. S. G., Barak, L. S., Menard, L., Caron, M. G. (1996) Dynamin and beta-arrestin reveal distinct mechanisms for G protein-coupled receptor internalization. J. Biol. Chem. 271,18302-18305[Abstract/Free Full Text]
  49. Prossnitz, E. R., Ye, R. D. (1997) The N-formyl peptide receptor: a model for the study of chemoattractant receptor structure and function. Pharmacol. Ther. 74,73-102[Medline]
  50. Bennett, T. A., Maestas, D. C., Prossnitz, E. R. (2000) Arrestin binding to the G protein-coupled N-formyl peptide receptor is regulated by the conserved ‘DRY’sequence. J. Biol. Chem. 275,24590-24604[Abstract/Free Full Text]
  51. Mackenzie, I. R., Hao, C., Munoz, D. G. (1995) Role of microglia in senile plaque formation. Neurobiol. Aging 16,797-804[Medline]
  52. Sturchler-Pierrat, C., Abramowski, D., Duke, M., Wiederhold, K. H., Mistl, C., Rothacher, S., Ledermann, B., Burki, K., Frey, P., Paganetti, P. A., Waridel, C., Calhoun, M. E., Jucker, M., Probst, A., Staufenbiel, M., Sommer, B. (1997) Two amyloid precursor protein transgenic mouse models with Alzheimer disease-like pathology. Proc. Natl. Acad. Sci. USA 94,13287-13292[Abstract/Free Full Text]
  53. Mills, J., Reiner, P. B. (1999) Regulation of amyloid precursor protein cleavage. J. Neurochem. 72,443-460[Medline]
  54. Shaffer, L. M., Dority, M. D., Gupta-Bansal, R., Frederickson, R. C., Younkin, S. G., Brunden, K. R. (1995) Amyloid beta protein (A beta) removal by neuroglial cells in culture. Neurobiol. Aging 16,737-745[Medline]
  55. Chung, H., Brazil, M. I., Soe, T. T., Maxfield, F. R. (1999) Uptake, degradation, and release of fibrillar and soluble forms of Alzheimer’s amyloid beta-peptide by microglial cells. J. Biol. Chem. 274,32301-32308[Abstract/Free Full Text]
  56. Weltzien, R. B., Pachter, J. S. (2000) Visualization of beta-amyloid peptide (Abeta) phagocytosis by human mononuclear phagocytes: dependency on Abeta aggregate size. J. Neurosci. Res. 59,522-527[Medline]
  57. DeWitt, D. A., Perry, G., Cohen, M., Doller, C., Silver, J. (1998) Astrocytes regulate microglial phagocytosis of senile plaque cores of Alzheimer’s disease. Exp. Neurol. 149,329-340[Medline]
  58. Schenk, D., Barbour, R., Dunn, W., Gordon, G., Grajeda, H., Guido, T., Hu, K., Huang, J., Johnson-Wood, K., Khan, K., Kholodenko, D., Lee, M., Liao, Z., Lieberburg, I., Motter, R., Mutter, L., Soriano, F., Shopp, G., Vasquez, N., Vandevert, C., Walker, S., Wogulis, M., Yednock, T., Games, D., Seubert, P. (1999) Immunization with amyloid-beta attenuates Alzheimer-disease-like pathology in the PDAPP mouse. Nature (London) 400,173-177[Medline]



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