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Endocytosed 2-Microglobulin Amyloid Fibrils Induce Necrosis and Apoptosis of Rabbit Synovial Fibroblasts by Disrupting Endosomal/Lysosomal Membranes: A Novel Mechanism on the Cytotoxicity of Amyloid Fibrils.

Okoshi T, Yamaguchi I, Ozawa D, Hasegawa K, Naiki H - PLoS ONE (2015)

Bottom Line: Dialysis-related amyloidosis is a major complication in long-term hemodialysis patients.As compared to β2-m monomers and vehicle buffer, β2-m amyloid fibrils significantly reduced cellular viability as measured by the lactate dehydrogenase release assay and the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay and significantly increased the percentage of apoptotic cells as measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling method. β2-m amyloid fibrils added to the medium adhered to cell surfaces, but did not disrupt artificial plasma membranes as measured by the liposome dye release assay.These results suggest that endocytosed β2-m amyloid fibrils induce necrosis and apoptosis by disrupting endosomal/lysosomal membranes, and this novel mechanism on the cytotoxicity of amyloid fibrils is described.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Pathology, Department of Pathological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui, Japan.

ABSTRACT
Dialysis-related amyloidosis is a major complication in long-term hemodialysis patients. In dialysis-related amyloidosis, β2-microglobulin (β2-m) amyloid fibrils deposit in the osteoarticular tissue, leading to carpal tunnel syndrome and destructive arthropathy with cystic bone lesions, but the mechanism by which these amyloid fibrils destruct bone and joint tissue is not fully understood. In this study, we assessed the cytotoxic effect of β2-m amyloid fibrils on the cultured rabbit synovial fibroblasts. Under light microscopy, the cells treated with amyloid fibrils exhibited both necrotic and apoptotic changes, while the cells treated with β2-m monomers and vehicle buffer exhibited no morphological changes. As compared to β2-m monomers and vehicle buffer, β2-m amyloid fibrils significantly reduced cellular viability as measured by the lactate dehydrogenase release assay and the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay and significantly increased the percentage of apoptotic cells as measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling method. β2-m amyloid fibrils added to the medium adhered to cell surfaces, but did not disrupt artificial plasma membranes as measured by the liposome dye release assay. Interestingly, when the cells were incubated with amyloid fibrils for several hours, many endosomes/lysosomes filled with amyloid fibrils were observed under confocal laser microscopy and electron microscopy, Moreover, some endosomal/lysosomal membranes were disrupted by intravesicular fibrils, leading to the leakage of the fibrils into the cytosol and adjacent to mitochondria. Inhibition of actin-dependent endocytosis by cytochalasin D attenuated the toxicity of amyloid fibrils. These results suggest that endocytosed β2-m amyloid fibrils induce necrosis and apoptosis by disrupting endosomal/lysosomal membranes, and this novel mechanism on the cytotoxicity of amyloid fibrils is described.

No MeSH data available.


Related in: MedlinePlus

β2-m amyloid fibrils are internalized and sorted to lysosomes.HIG-82 cells incubated with Ham’s F12 medium containing vehicle buffer, 10 μg/ml β2-m monomer, or 10 μg/ml β2-m fibrils for 12 hrs were stained for lysosomes (red), β2-m (green), and nuclei (blue), and observed with the confocal laser microscope as described in Materials and Methods. When the cells were incubated with fibrils (right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Importantly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes. The scale bars are 10 μm long.
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pone.0139330.g006: β2-m amyloid fibrils are internalized and sorted to lysosomes.HIG-82 cells incubated with Ham’s F12 medium containing vehicle buffer, 10 μg/ml β2-m monomer, or 10 μg/ml β2-m fibrils for 12 hrs were stained for lysosomes (red), β2-m (green), and nuclei (blue), and observed with the confocal laser microscope as described in Materials and Methods. When the cells were incubated with fibrils (right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Importantly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes. The scale bars are 10 μm long.

Mentions: To examine the possibility that β2-m amyloid fibrils are endocytosed and sorted to lysosomes by HIG-82 cells, we next performed lysotracker staining and indirect immunofluorescence for β2-m, followed by confocal laser microscopy as described in Materials and Methods (Fig 6). When the cells were incubated with fibrils (Fig 6, right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Interestingly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes, indicating that β2-m fibrils were carried by the endosomal-lysosomal pathway.


Endocytosed 2-Microglobulin Amyloid Fibrils Induce Necrosis and Apoptosis of Rabbit Synovial Fibroblasts by Disrupting Endosomal/Lysosomal Membranes: A Novel Mechanism on the Cytotoxicity of Amyloid Fibrils.

Okoshi T, Yamaguchi I, Ozawa D, Hasegawa K, Naiki H - PLoS ONE (2015)

β2-m amyloid fibrils are internalized and sorted to lysosomes.HIG-82 cells incubated with Ham’s F12 medium containing vehicle buffer, 10 μg/ml β2-m monomer, or 10 μg/ml β2-m fibrils for 12 hrs were stained for lysosomes (red), β2-m (green), and nuclei (blue), and observed with the confocal laser microscope as described in Materials and Methods. When the cells were incubated with fibrils (right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Importantly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes. The scale bars are 10 μm long.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4589361&req=5

pone.0139330.g006: β2-m amyloid fibrils are internalized and sorted to lysosomes.HIG-82 cells incubated with Ham’s F12 medium containing vehicle buffer, 10 μg/ml β2-m monomer, or 10 μg/ml β2-m fibrils for 12 hrs were stained for lysosomes (red), β2-m (green), and nuclei (blue), and observed with the confocal laser microscope as described in Materials and Methods. When the cells were incubated with fibrils (right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Importantly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes. The scale bars are 10 μm long.
Mentions: To examine the possibility that β2-m amyloid fibrils are endocytosed and sorted to lysosomes by HIG-82 cells, we next performed lysotracker staining and indirect immunofluorescence for β2-m, followed by confocal laser microscopy as described in Materials and Methods (Fig 6). When the cells were incubated with fibrils (Fig 6, right column), green fluorescence indicating β2-m fibrils were observed inside the cells in a granular pattern, as well as on the surface of the cells. Interestingly, some green-colored granules containing β2-m fibrils were merged with red-colored lysosomes, indicating that β2-m fibrils were carried by the endosomal-lysosomal pathway.

Bottom Line: Dialysis-related amyloidosis is a major complication in long-term hemodialysis patients.As compared to β2-m monomers and vehicle buffer, β2-m amyloid fibrils significantly reduced cellular viability as measured by the lactate dehydrogenase release assay and the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay and significantly increased the percentage of apoptotic cells as measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling method. β2-m amyloid fibrils added to the medium adhered to cell surfaces, but did not disrupt artificial plasma membranes as measured by the liposome dye release assay.These results suggest that endocytosed β2-m amyloid fibrils induce necrosis and apoptosis by disrupting endosomal/lysosomal membranes, and this novel mechanism on the cytotoxicity of amyloid fibrils is described.

View Article: PubMed Central - PubMed

Affiliation: Division of Molecular Pathology, Department of Pathological Sciences, Faculty of Medical Sciences, University of Fukui, Fukui, Japan.

ABSTRACT
Dialysis-related amyloidosis is a major complication in long-term hemodialysis patients. In dialysis-related amyloidosis, β2-microglobulin (β2-m) amyloid fibrils deposit in the osteoarticular tissue, leading to carpal tunnel syndrome and destructive arthropathy with cystic bone lesions, but the mechanism by which these amyloid fibrils destruct bone and joint tissue is not fully understood. In this study, we assessed the cytotoxic effect of β2-m amyloid fibrils on the cultured rabbit synovial fibroblasts. Under light microscopy, the cells treated with amyloid fibrils exhibited both necrotic and apoptotic changes, while the cells treated with β2-m monomers and vehicle buffer exhibited no morphological changes. As compared to β2-m monomers and vehicle buffer, β2-m amyloid fibrils significantly reduced cellular viability as measured by the lactate dehydrogenase release assay and the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay and significantly increased the percentage of apoptotic cells as measured by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling method. β2-m amyloid fibrils added to the medium adhered to cell surfaces, but did not disrupt artificial plasma membranes as measured by the liposome dye release assay. Interestingly, when the cells were incubated with amyloid fibrils for several hours, many endosomes/lysosomes filled with amyloid fibrils were observed under confocal laser microscopy and electron microscopy, Moreover, some endosomal/lysosomal membranes were disrupted by intravesicular fibrils, leading to the leakage of the fibrils into the cytosol and adjacent to mitochondria. Inhibition of actin-dependent endocytosis by cytochalasin D attenuated the toxicity of amyloid fibrils. These results suggest that endocytosed β2-m amyloid fibrils induce necrosis and apoptosis by disrupting endosomal/lysosomal membranes, and this novel mechanism on the cytotoxicity of amyloid fibrils is described.

No MeSH data available.


Related in: MedlinePlus