Amyloid is a term for extracellular protein fibril deposits that have characteristic tinctorial and structural properties. Heparan sulphate, or the heparan sulphate proteoglycan perlecan, has been identified in all amyloids and implicated in the earliest stages of inflammation-associated (AA) amyloid induction. Heparan sulphate interacts with the AA amyloid precursor and the beta-peptide of Alzheimer's amyloid, imparting characteristic secondary and tertiary amyloid structural features. These observations suggest that molecules that interfere with this interaction may prevent or arrest amyloidogenesis. We synthesized low-molecular-weight (135-1,000) anionic sulphonate or sulphate compounds. When administered orally, these compounds substantially reduced murine splenic AA amyloid progression. They also interfered with heparan sulphate-stimulated beta-peptide fibril aggregation in vitro.

Aims/hypothesis Islet amyloid in type 2 diabetes contributes to loss of beta cell mass and function. Since islets are susceptible to oxidative stress-induced toxicity, we sought to determine whether islet amyloid formation is associated with induction of oxidative stress. Methods Human islet amyloid polypeptide transgenic and non-transgenic mouse islets were cultured for 48 or 144 h with or without the antioxidant N-acetyl-L-cysteine (NAC) or the amyloid inhibitor Congo Red. Amyloid deposition, reactive oxygen species (ROS) production, beta cell apoptosis, and insulin secretion, content and mRNA were measured.Results After 48 h, amyloid deposition was associated with increased ROS levels and increased beta cell apoptosis, but no change in insulin secretion, content or mRNA levels. Antioxidant treatment prevented the rise in ROS, but did not prevent amyloid formation or beta cell apoptosis. In contrast, inhibition of amyloid formation prevented the induction of oxidative stress and beta cell apoptosis. After 144 h, amyloid deposition was further increased and was associated with increased ROS levels, increased beta cell apoptosis and decreased insulin content. At this time-point, antioxidant treatment and inhibition of amyloid formation were effective in reducing ROS levels, amyloid formation and beta cell apoptosis. Inhibition of amyloid formation also increased insulin content. Conclusions/interpretation Islet amyloid formation induces oxidative stress, which in the short term does not mediate beta cell apoptosis, but in the longer term may feed back to further exacerbate amyloid formation and contribute to beta cell apoptosis.

The glycosaminoglycan, heparan sulfate (HS), binds proteins to modulate signaling events in embryogenesis. All identified protein-binding HS epitopes contain L-iduronic acid (IdoA). We report that targeted disruption of the murine D-glucuronyl C5-epimerase gene results in a structurally altered HS lacking IdoA. The corresponding phenotype is lethal, with renal agenesis, lung defects, and skeletal malformations. Unexpectedly, major organ systems, including the brain, liver, gastrointestinal tract, skin, and heart, appeared normal. We find that IdoA units are essential for normal kidney, lung, and skeletal development, albeit with different requirement for 2-Osulfation. By contrast, major early developmental events known to critically depend on heparan sulfate apparently proceed normally even in the absence of IdoA.

Serum amyloid A (SAA), a protein originally of interest primarily to investigators focusing on AA amyloidogenesis, has become a subject of interest to a very broad research community. SAA is still a major amyloid research topic because AA amyloid, for which SAA is the precursor, is the prototypic model of in vivo amyloidogenesis and much that has been learned with this model has been applicable to much more common clinical types of amyloid. However, SAA has also become a subject of considerable interest to those studying (i) the synthesis and regulation of acute phase proteins, of which SAA is a prime example, (ii) the role that SAA plays in tissue injury and inflammation, a situation in which the plasma concentration of SAA may increase a 1000-fold, (iii) the influence that SAA has on HDL structure and function, because during inflammation the majority of SAA is an apolipoprotein of HDL, (iv) the influence that SAA may have on HDL's role in reverse cholesterol transport, and therefore, (v) SAA's potential role in atherogenesis. However, no physiological role for SAA, among many proposed, has been widely accepted. None the less from an evolutionary perspective SAA must have a critical physiological function conferring survival-value because SAA genes have existed for at least 500 million years and SAA's amino acid sequence has been substantially conserved. An examination of the published literature over the last 40 years reveals a great deal of conflicting data and interpretation. Using SAA's conserved amino acid sequence and the physiological effects it has while in its native structure, namely an HDL apolipoprotein, we argue that much of the confounding data and interpretation relates to experimental pitfalls not appreciated when working with SAA, a failure to appreciate the value of physiologic studies done in the 1970-1990 and a current major focus on putative roles of SAA in atherogenesis and chronic disease. When viewed from an evolutionary perspective, published data suggest that acute-phase SAA is part of a systemic response to injury to recycle and reuse cholesterol from destroyed and damaged cells. This is accomplished through SAA's targeted delivery of HDL to macrophages, and its suppression of ACAT, the enhancement of neutral cholesterol esterase and ABC transporters in macrophages. The recycling of cholesterol during serious injury, when dietary intake is restricted and there is an immediate and critical requirement of cholesterol in the generation of myriads of cells involved in inflammation and repair responses, is likely SAA's important survival role. Data implicating SAA in atherogenesis are not relevant to its evolutionary role. Furthermore, in apoE(-/-) mice, domains near the N- and C- termini of SAA inhibit the initiation and progression of aortic lipid lesions illustrating the conflicting nature of these two sets of data.

Amyloid diseases encompass >20 medical disorders that include amyloid protein A (AA) amyloidosis, Alzheimer's disease, and type 2 diabetes. A common feature of these conditions is the selective organ deposition of disease-specific fibrillar proteins, along with the sulfated glycosaminoglycan, heparan sulfate. We have generated transgenic mice that overexpress human heparanase and have tested their susceptibility to amyloid induction. Drastic shortening of heparan sulfate chains was observed in heparanaseoverproducing organs, such as liver and kidney. These sites selectively escaped amyloid deposition on experimental induction of inflammation-associated AA amyloidosis, as verified by lack of material staining with Congo Red, as well as lack of associated polysaccharide, whereas the same tissues from control animals were heavily infiltrated with amyloid. By contrast, the spleens of transgenic mice that failed to significantly overexpress heparanase contained heparan sulfate chains similar in size to those of control spleen and remained susceptible to amyloid deposition. Our findings provide direct in vivo evidence that heparan sulfate is essential for the development of amyloid disease.inflammation ͉ transgenic mice ͉ endo-glucuronidase ͉ Congo red staining