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Immunohistochemical detection of haem oxygenase in AA amyloidogenesis.

Published Article
Journal of electron microscopy
Publication Date
PMID: 15582941


Haem oxygenase (HO)-1, a rate-limiting enzyme in the degradation of haem, is increased in Alzheimer's disease and in inflammations such as AA amyloidosis. However, the specific association of HO-1 is poorly understood in AA amyloidosis. In this study, we designed the experiment to reveal the contribution and association of HO-1 in the spleen during experimental murine AA amyloidosis. Experimental murine AA amyloidosis was induced with injection of an emulsion consisting of Freund's complete adjuvant and Mycobacterium butyricum. The serum amyloid A level was highest on day 3. The distribution of cells containing iron, indicating an increase of HO-1 in the red pulp, was detected with Berlin blue staining. AA amyloid formation was immunohistochemically detected as a marker by chondroitin sulphate proteoglycan (CSPG), one of the components of AA amyloid fibrils. Immunolocalizations of HO-1 and CSPG indicated a conspicuous increase and scattering of positive cells in the red pulp of the spleen. Double positive cells were not detected. On day 7, amyloid deposition was detected with Congo red staining in the extracellular spaces in the marginal zone of the white pulp in the spleen and HO-1-positive cells accumulated near the amyloid deposition area. CSPG was detected within the cells and also localized in the amyloid deposition area. CSPG was still not localized in the HO-1-positive cells. Double positive cells of HO-1 and CSPG were localized in the red pulp and in the amyloid deposition area on day 14. X-ray microanalysis indicated the existence of iron in the electron-dense bodies of fibroblasts in the amyloid deposition areas. The fibroblasts extended amyloid fibrils into the extracellular spaces of the marginal zone. These results suggest that HO-1-positive fibroblasts, but not HO-1-positive macrophages, are associated with the late stage of amyloid fibril formation.


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