heparitin-sulfate and Splenic-Diseases

An essential and distinguishing feature of all amyloids is the presence of fibrillar structures of approximately 10-nm width. The precise nature of the fibril is not yet clearly understood, particularly in situ, and the ultrastructure of isolated fibrils differs significantly from that of fibrils observed in situ. The fibrils are generally believed to be composed of a protein specific to each type of amyloid, but increasing evidence suggests additional associations with other components such as heparan sulfate proteoglycan (HSPG) and amyloid P component (AP). Experimental AA amyloidosis was induced in mice by amyloid enhancing factor and an inflammatory stimulus (subcutaneous AgNO3); fibrils were thereafter examined in detail. Particular attention was paid to ultrastructural characteristics known to represent particular molecular components of basement membranes such as HSPG and AP. Additionally, rabbit anti-mouse AA antisera was used with 5-nm and 1-nm gold particles to establish the location of the AA protein in-situ. Amyloid fibrils could be identified in their mature form as well as at apparent intermediate stages of formation. The fibril contained an apparent core which is composed of an assembly of 3.5-nm wide pentosomal particles having the characteristics of AP. Wound around the AP assembly in a helical fashion is a "double tracked" ribbon-like entity, 3 nm wide, having the morphologic characteristics of chondroitin sulfate proteoglycan (CSPG). Covering the surface of this structure is a second ribbon-like double track structure, but this one is wider (4.6 nm vs 3.0 nm) than the CSPG. These have the ultrastructural characteristics of HSPG. Routine fixation and tissue preparation techniques that usually remove HSPG from microfibrils did not do so with amyloid fibrils, suggesting an alteration in affinity between these components. The AA protein could be identified as a 1 - to 2-nm filament network on the most exterior surface of the fibril. The ultrastructure of AA amyloid fibrils in situ resembles that of connective tissue microfibrils, and, in addition to AA protein, is likely composed of HSPG, CSPG, and AP. Amyloid fibrils can be distinguished from microfibrils by the apparently stronger binding of HSPG to the surface of the amyloid fibril and the presence of the AA filaments. A model of the in situ organization of AA amyloid fibrils is proposed.

Topics: Amyloidosis; Animals; Chondroitin Sulfate Proteoglycans; Disease Models, Animal; Female; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Mice; Microscopy, Electron; Microscopy, Immunoelectron; Proteoglycans; Rabbits; Serum Amyloid A Protein; Serum Amyloid P-Component; Splenic Diseases

In a murine model of AA amyloidosis, it has been demonstrated that perlecan, the basement membrane heparan sulfate proteoglycan, is co-deposited with AA amyloid as it forms in various tissues. The objectives of this study were to determine whether the accumulation of perlecan during amyloidogenesis is associated with induction of perlecan gene expression and, if so, to define the temporal relationship of this induction to the onset of amyloid formation.. Accelerated splenic AA amyloidosis was stimulated in mice by concomitant administration of subcutaneous silver nitrate as an inflammatory stimulus and amyloid-enhancing factor. A kinetic analysis of splenic perlecan mRNA levels during amyloid formation in the spleen was conducted using a reverse transcription-polymerase chain reaction assay. Amyloid deposits were detected histochemically with the Congo red stain and by immunohistochemistry using anti-AA antisera.. Perlecan mRNA levels increased significantly during amyloidogenesis, increasing 4.1-fold within 72 hours of the amyloidogenic stimulus and subsequently falling to steady-state levels. A 2.0-fold induction of perlecan mRNA occurred by 24 hours post-stimulation, a time at which amyloid was not detectable by either histochemistry or immunohistochemistry. In contrast, control animals administered either the inflammatory stimulus or AEF alone showed no significant change in perlecan mRNA levels.. Increased perlecan mRNA levels account, at least in part, for the accumulation of perlecan in murine splenic AA amyloid deposits. This induction of perlecan gene expression occurs before the onset of amyloid formation, supporting a role for perlecan in the earliest stages of amyloid fibrillogenesis.

Topics: Amyloid; Amyloidosis; Animals; Base Sequence; DNA Primers; Female; Gene Expression; Gene Expression Regulation; Glycoproteins; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Kinetics; Mice; Molecular Sequence Data; Oligonucleotides, Antisense; Polymerase Chain Reaction; Proteoglycans; RNA, Messenger; Silver Nitrate; Spleen; Splenic Diseases

Highly sulfated glycosaminoglycans (GAG) have been demonstrated in every form of amyloid examined to date. Based on temporal studies in murine amyloidogenesis heparan sulfate is deposited coincidentally with the amyloid protein. Our purpose was to follow in vivo GAG synthesis by monitoring 35SO4 incorporation during amyloidogenesis. Several necessary previously unexamined nonamyloidogenic controls were also examined.. Murine splenic amyloid was induced with lipopolysaccharide (LPS) and amyloid enhancing factor (AEF). Splenic GAG synthesis was monitored by 35SO4 incorporation. Corrections were made for alterations in SO4 metabolism which occur during inflammation.. All animals with an inflammatory reaction had a marked increase in GAG synthesis. Those animals receiving AEF, or AEF+LPS, had a significant increase in heparan sulfate synthesis. This was particularly profound in the group developing amyloid (i.e., AEF+LPS).. Our results indicate that critical factors in amyloid deposition include quantitative as well as qualitative changes that take place in tissue GAG synthesis. A distinct metabolic effect of AEF is demonstrated for the first time.

Topics: Acute Disease; Amyloid; Amyloidosis; Animals; Glycoproteins; Glycosaminoglycans; Heparitin Sulfate; Lipopolysaccharides; Mice; Protein Precursors; Spleen; Splenic Diseases; Sulfates; Sulfur Radioisotopes