Therapeutic effect of sulphated hyaluronic acid, a potential selectin-blocking agent, on experimental progressive mesangial proliferative glomerulonephritis

Analogues of the pan-selectin antagonist rivipansel (GMI-1070)

The selectin family consisting of E-, P- and L-selectin plays dominant roles in atherosclerosis, ischemia-reperfusion injury, inflammatory diseases, and metastatic spreading of some cancers. An early goal in selectin-targeted drug discovery campaigns was to identify ligands binding to all three selectins, so-called pan-selectin antagonists. The physiological epitope, tetrasaccharide sialyl Lewisx (sLex, 1) binds to all selectins, albeit with very different affinities. Whereas P- and L-selectin require additional interactions contributed by sulfate groups for high binding affinity, E-selectin can functionally bind sLex-modified glycolipids and glycoproteins. Rivipansel (3) marked the first pan-selectin antagonist, which simultaneously interacted with both the sLex and the sulfate binding site. The aim of this contribution was to improve the pan-selectin affinity of rivipansel (3) by leveraging a new class of sLex mimetics in combination with an optimized linker length to the sulfate bearing group. As a result, the pan-selectin antagonist 11b exhibits an approximatively 5-fold improved affinity for E-, as well as P-selectin.

An Oligomeric Sulfated Hyaluronan and Silk-Elastinlike Polymer Combination Protects against Murine Radiation Induced Proctitis

Semisynthetic glycosaminoglycan ethers (SAGEs) are short, sulfated hyaluronans which combine the natural properties of hyaluronan with chemical sulfation. In a murine model, SAGEs provide protection against radiation induced proctitis (RIP), a side effect of lower abdominal radiotherapy for cancer. The anti-inflammatory effects of SAGE have been studied in inflammatory diseases at mucosal barrier sites; however, few mechanisms have been uncovered necessitating high throughput methods. SAGEs were combined with silk-elastinlike polymers (SELPs) to enhance rectal accumulation in mice. After high radiation exposure to the lower abdominal area, mice were followed for 3 days or until they met humane endpoints, before evaluation of behavioral pain responses and histological assessment of rectal inflammation. RNA sequencing was conducted on tissues from the 3-day cohort to determine molecular mechanisms of SAGE–SELP. After 3 days, mice receiving the SAGE–SELP combination yielded significantly lowered pain responses and amelioration of radiation-induced rectal inflammation. Mice receiving the drug–polymer combination survived 60% longer than other irradiated mice, with a fraction exhibiting long term survival. Sequencing reveals varied regulation of toll like receptors, antioxidant activities, T-cell signaling, and pathways associated with pain. This investigation elucidates several molecular mechanisms of SAGEs and exhibits promising measures for prevention of RIP.

Thermogels containing sulfated hyaluronan as novel topical therapeutics for treatment of ocular surface inflammation

The development of long lasting therapeutic agents is critically important for efficient treatment of chronic diseases. We herein report a rational strategy to develop a therapeutic thermogel featured with prolonged anti-inflammatory and corneal-protective effects. Specifically, a hyaluronic acid with different sulfation degrees and an amine-terminated poly(N-isopropylacrylamide) are conjugated to achieve the thermogels. In vitro studies reveal that the thermogels are highly biocompatible to statens seruminstitut rabbit cornea cells and their anti-inflammatory properties are strongly dependent on the sulfation degree. In a rabbit model of ocular inflammation, single-dose topical administration of a thermogel formulation could repair defects in corneal epithelium (∼99% thickness restored), prevent corneal cell apoptosis (∼68.3% cells recovered), and suppress ocular surface inflammation (∼4-fold decrease) for a follow-up period of 7 days. This high treatment efficacy of the thermogel can be attributed to its potent inhibition in selectin-mediated leukocyte infiltration as well as effective corneal protection. These findings show a great promise for topical treatment of ocular inflammation and advancement of ophthalmic formulations using the bioactive thermogel as a therapeutic component that is not rapidly cleared from the eye and thus considerably reduces administration times.

•

Sulfated hyaluronan thermogels served as intrinsic therapeutic agents.

•

Thermogels exert inhibitory effects on selectin-mediated leukocyte infiltration.

•

Sulfation degree is a key to achieve superior therapeutic thermogels.

•

Highly sulfated agent reveals potent anti-inflammatory/corneal-protective effects.

•

Single dose reduces corneal inflammation by 4-folds at 7 days post-instillation.

Hyaluronan as a therapeutic target in human diseases

Accumulation and turnover of extracellular matrix is a hallmark of tissue injury, repair and remodeling in human diseases. Hyaluronan is a major component of the extracellular matrix and plays an important role in regulating tissue injury and repair, and controlling disease outcomes. The function of hyaluronan depends on its size, location, and interactions with binding partners. While fragmented hyaluronan stimulates the expression of an array of genes by a variety of cell types regulating inflammatory responses and tissue repair, cell surface hyaluronan provides protection against tissue damage from the environment and promotes regeneration and repair. The interactions of hyaluronan and its binding proteins participate in the pathogenesis of many human diseases. Thus, targeting hyaluronan and its interactions with cells and proteins may provide new approaches to developing therapeutics for inflammatory and fibrosing diseases. This review focuses on the role of hyaluronan in biological and pathological processes, and as a potential therapeutic target in human diseases.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

Fucosylated chondroitin sulfate attenuates renal fibrosis in animals submitted to unilateral ureteral obstruction: a P-selectin-mediated event?

Fibrosis is the end point of most renal diseases, and several glycosaminoglycans have been shown to attenuate this process. Marine invertebrate glycosaminoglycans with unique structures have opened the possibility to test these new compounds on renal fibrosis. The effect of a fucosylated chondroitin sulfate from an echinoderm marine species is reported with the use of a model of renal fibrosis in rats, termed unilateral ureteral obstruction. Animals were given 4 mg/kg body wt of fucosylated chondroitin sulfate intraperitoneally, once a day. After 14 days, their kidneys were examined by histological, immunohistochemical, and biochemical methods. Compared with control mice, collagen deposition decreased in the course of renal fibrosis in the animals receiving fucosylated chondroitin sulfate, as revealed by Sirius red staining and hydroxyproline content. The cellularity related to myofibroblasts and macrophages was also reduced, as was the production of transforming growth factor (TGF)-β. The glycosaminoglycan content increased in the renal interstitium of animals submitted to unilateral ureteral obstruction compared with the control contralateral kidney, mostly due to an increase of chondroitin sulfate content. Interestingly, no change in the pattern of glycosaminoglycan deposition was observed after administration of fucosylated chondroitin sulfate. Fibrosis induced by unilateral ureteral obstruction is attenuated in P-selectin-deficient mice, which also do not respond to the invertebrate glycosaminoglycan. In conclusion, fucosylated chondroitin sulfate attenuates renal fibrosis on a ureteral obstruction model in mice preponderantly through a P-selectin-mediated mechanism.

From carbohydrate leads to glycomimetic drugs

Carbohydrates are the most abundant natural products. Besides their role in metabolism and as structural building blocks, they are fundamental constituents of every cell surface, where they are involved in vital cellular recognition processes. Carbohydrates are a relatively untapped source of new drugs and therefore offer exciting new therapeutic opportunities. Advances in the functional understanding of carbohydrate-protein interactions have enabled the development of a new class of small-molecule drugs, known as glycomimetics. These compounds mimic the bioactive function of carbohydrates and address the drawbacks of carbohydrate leads, namely their low activity and insufficient drug-like properties. Here, we examine examples of approved carbohydrate-derived drugs, discuss the potential of carbohydrate-binding proteins as new drug targets (focusing on the lectin families) and consider ways to overcome the challenges of developing this unique class of novel therapeutics.

Excreted urinary mediators in an animal model of experimental immune nephritis with potential pathogenic significance

OBJECTIVE

Currently, proteinuria is viewed as the earliest indicator of renal disease in immune-mediated nephritis. The objective of this study was to determine whether additional mediators may be excreted in the urine during immune-mediated nephritis, using an experimental model with a well-defined disease course.

METHODS

Urine samples from mice with anti-glomerular basement membrane (anti-GBM) antibody-induced experimental nephritis were screened using a focused immunoproteome array bearing 62 cytokines/chemokines/soluble receptors. Molecules identified through this screening assay were validated using an enzyme-linked immunosorbent assay. One of these molecules was further evaluated for its pathogenic role in disease, using antibody-blocking studies.

RESULTS

Compared with B6 and BALB/c mice, in which moderately severe immune-mediated nephritis develops, the highly nephritis-susceptible 129/Sv and DBA/1 mice exhibited significantly increased urinary levels of vascular cell adhesion molecule 1 (VCAM-1), P-selectin, tumor necrosis factor receptor I (TNFRI), and CXCL16, particularly at the peak of disease. Whereas some of the mediators appeared to be serum derived early in the disease course, local production in the kidneys appeared to be an important source of these mediators later in the course of disease. Both intrinsic renal cells and infiltrating leukocytes appeared to be capable of producing these mediators. Finally, antibody-mediated blocking of CXCL16 ameliorated experimental immune nephritis.

CONCLUSION

These studies identified VCAM-1, P-selectin, TNFRI, and CXCL16 as a quartet of molecules that have potential pathogenic significance; the levels of these molecules are significantly elevated during experimental immune nephritis. The relevance of these molecules in spontaneous immune nephritis warrants investigation.

Sulfated Hyaluronic Acid, a Potential Selectin Inhibitor, Ameliorates Experimentally Induced Crescentic Glomerulonephritis

BACKGROUND/AIMS

Sulfated polysaccharides are known to interfere with the binding of selectins and their ligands. Recently, we demonstrated that sulfated hyaluronic acid (SHA), a synthetic sulfated polysaccharide, showed preventive and therapeutic effects on experimental mesangial proliferative glomerulonephritis. Here we evaluated the protective potential of SHA on crescentic glomerulonephritis, using nephrotoxic serum (NTS) nephritis in Wistar-Kyoto (WKY) rats.

METHODS

Crescentic glomerulonephritis was induced by injection of NTS in WKY rats. Rats subsequently received intraperitoneal administration of SHA (0.5 or 1.5 mg/kg/day) or non-sulfated hyaluronic acid (HA) (1.5 mg/kg/day) for 14 days. The urinary protein excretion was measured, and expression of selectins, intraglomerular leukocytes and crescent formation were examined by immunohistochemistry. In addition, we examined the urinary protein excretion of SHA (1.5 mg/kg/day) administered from day 7 after the induction of crescentic glomerulonephritis.

RESULTS

The expression of P-selectin was increased in the glomerulus of crescentic glomerulonephritis. SHA reduced proteinuria, macrophage infiltration, and crescent formation in a dose-dependent manner. Furthermore, administration of SHA (1.5 mg/kg/day) from day 7 also reduced the urinary protein excretion on day 14 compared with that in saline and HA group.

CONCLUSION

Our results suggest that SHA inhibits intraglomerular infiltration of macrophages, and prevents progression of experimental crescentic glomerulonephritis. Sulfated polysaccharides might be beneficial for the treatment of crescentic glomerulonephritis.

Heparan sulfate proteoglycans in glomerular inflammation

Heparan sulfate proteoglycans (HSPGs) are glycoproteins consisting of a core protein to which linear heparan sulfate side chains are covalently attached. These heparan sulfate side chains can be modified at different positions by several enzymes, which include N-deacetylases, N- and O-sulfotransferases, and an epimerase. These heparan sulfate modifications give rise to an enormous structural diversity, which corresponds to the variety of biologic functions mediated by heparan sulfate, including its role in inflammation. The HSPGs in the glomerular basement membrane (GBM), perlecan, agrin, and collagen XVIII, play an important role in the charge-selective permeability of the glomerular filter. In addition to these HSPGs, various cell types express HSPGs at their cell surface, which include syndecans, glypicans, CD44, and betaglycan. During inflammation, HSPGs, especially heparan sulfate, in the extracellular matrix (ECM) and at the surface of endothelial cells bind chemokines, which establishes a local concentration gradient recruiting leukocytes. Endothelial and leukocyte cell surface HSPGs also play a role in their direct adhesive interactions via other cell surface adhesion molecules, such as selectins and beta2 integrin. Activated leukocytes and endothelial cells exert heparanase activity, resulting in degradation of heparan sulfate moieties in the ECM, which facilitates leukocyte passage into tissues and the release of heparan sulfate-bound factors. In various renal inflammatory diseases the expression of agrin and GBM-associated heparan sulfate is decreased, while the expression of CD44 is increased. Heparan sulfate or heparin preparations affect inflammatory cell behavior and have promising therapeutic, anti-inflammatory properties by preventing leukocyte adhesion/influx and tissue damage.