Effects of Heparin and Enoxaparin on APP Processing and Aβ Production in Primary Cortical Neurons from Tg2576 Mice

Alzheimer's disease (AD) is caused by accumulation of Aβ, which is produced through sequential cleavage of β-amyloid precursor protein (APP) by the β-site APP cleaving enzyme (BACE1) and γ-secretase. Enoxaparin, a low molecular weight form of the glycosaminoglycan (GAG) heparin, has been reported to lower Aβ plaque deposition and improve cognitive function in AD transgenic mice

Heparan sulfate accumulation with Abeta deposits in Alzheimer's disease and Tg2576 mice is contributed by glial cells.

Contains fulltext : 70077.pdf (Publisher’s version ) (Closed access)Amyloid beta-peptide (Abeta) plaques, one of the major neuropathological lesions in Alzheimer's disease (AD), can be broadly subdivided into two morphological categories: neuritic and diffuse. Heparan sulfate (HS) and HS proteoglycans (HSPGs) are codeposits of multiple amyloidoses, including AD. Although HS has been considered a limiting factor in the initiation of amyloid deposition, the pathological implications of HS in Abeta deposits of AD remain unclear. In this study, immunohistochemistry combined with fluorescence and confocal microscopy was employed to gain deeper insight into the accumulation of HS with Abeta plaques in sporadic and familial AD. Here we demonstrate that HS preferentially accumulated around the Abeta40 dense cores of neuritic plaques, but was largely absent from diffuse Abeta42 plaques, suggesting that Abeta42 deposition may occur independently of HS. A codeposition pattern of HS with Abeta deposits in Tg2576 mice was also examined. We identified the membrane-bound HSPGs, glypican-1 (GPC1) and syndecan-3 (SDC3), in glial cells associated with Abeta deposits, proximal to sites of HS accumulation. In mouse primary glial cultures, we observed increased levels of GPC1 and SDC3 following Abeta stimulation. These results suggest that HS codeposits with Abeta40 in neuritic plaques and is mainly derived from glial cells

Mechanism of Amylin Fibrillization Enhancement by Heparin*

We characterized the interaction of amylin with heparin fragments of defined length, which model the glycosaminoglycan chains associated with amyloid deposits found in type 2 diabetes. Binding of heparin fragments to the positively charged N-terminal half of monomeric amylin depends on the concentration of negatively charged saccharides but is independent of oligosaccharide length. By contrast, amylin fibrillogenesis has a sigmoidal dependence on heparin fragment length, with an enhancement observed for oligosaccharides longer than four monomers and a leveling off of effects beyond 12 monomers. The length dependence suggests that the negatively charged helical structure of heparin electrostatically complements the positively charged surface of the fibrillar amylin cross-β structure. Fluorescence resonance energy transfer and total internal reflection fluorescence microscopy experiments indicate that heparin associates with amylin fibrils, rather than enhancing fibrillogenesis catalytically. Short heparin fragments containing two- or eight-saccharide monomers protect against amylin cytotoxicity toward a MIN6 mouse cell model of pancreatic β-cells

Heparan sulfate inhibitors and their therapeutic implications in inflammatory illnesses

Introduction: Heparan sulfate (HS) is a polysaccharide that is ubiquitously expressed on the cell surface and in the extracellular matrix and interacts with a wide variety of proteins to mediate numerous biological and pathological functions, including inflammation. Areas covered: The structural diversity and the multiple biological roles of HS in inflammation are discussed. HS is involved in the recruitment and attachment of leukocytes to the inflamed epithelium, the activation of chemokines and the transmigration of leukocytes to the underlying target tissue. The endoglycosidase heparanase plays a key role in the above processes via the degradation of HS. HS mimetics that inhibit heparanase and block HS-binding proteins have been shown to inhibit inflammation in multiple animal models. Expert opinion: HS plays important roles in many stages of the inflammation process, in particular the regulation of leukocyte extravasation. Compounds that can inhibit HS-protein interactions thus have considerable potential as anti-inflammatory therapeutics capable of simultaneously interfering with multiple steps of the inflammation process. There are a number of such compounds in various stages of clinical development for cancer, which should also find applications in inflammatory illnesses