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Heparin Mimetics: Their Therapeutic Potential.

ABSTRACT: Heparin mimetics are synthetic and semi-synthetic compounds that are highly sulfated, structurally distinct analogues of glycosaminoglycans. These mimetics are often rationally designed to increase potency and binding selectivity towards specific proteins involved in disease manifestations. Some of the major therapeutic arenas towards which heparin mimetics are targeted include: coagulation and thrombosis, cancers, and inflammatory diseases. Although Fondaparinux, a rationally designed heparin mimetic, is now approved for prophylaxis and treatment of venous thromboembolism, the search for novel anticoagulant heparin mimetics with increased affinity and fewer side effects remains a subject of research. However, increasingly, research is focusing on the non-anticoagulant activities of these molecules. Heparin mimetics have potential as anti-cancer agents due to their ability to: (1) inhibit heparanase, an endoglycosidase which facilitates the spread of tumor cells; and (2) inhibit angiogenesis by binding to growth factors. The heparin mimetic, PI-88 is in clinical trials for post-surgical hepatocellular carcinoma and advanced melanoma. The anti-inflammatory properties of heparin mimetics have primarily been attributed to their ability to interact with: complement system proteins, selectins and chemokines; each of which function differently to facilitate inflammation. The efficacy of low/non-anticoagulant heparin mimetics in animal models of different inflammatory diseases has been demonstrated. These findings, plus clinical data that indicates heparin has anti-inflammatory activity, will raise the momentum for developing heparin mimetics as a new class of therapeutic agent for inflammatory diseases.

SUBMITTER: Mohamed S

PROVIDER: S-EPMC5748635 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Heparin Mimetics: Their Therapeutic Potential.

Mohamed Shifaza S Coombe Deirdre R DR

Pharmaceuticals (Basel, Switzerland) 20171002 4

Heparin mimetics are synthetic and semi-synthetic compounds that are highly sulfated, structurally distinct analogues of glycosaminoglycans. These mimetics are often rationally designed to increase potency and binding selectivity towards specific proteins involved in disease manifestations. Some of the major therapeutic arenas towards which heparin mimetics are targeted include: coagulation and thrombosis, cancers, and inflammatory diseases. Although Fondaparinux, a rationally designed heparin m ...[more]

PMID: 28974047

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Project description:Human neutrophil elastase (HNE) is a serine protease that plays vital roles in inflammation, innate immune response, and tissue remodeling processes. HNE has been actively pursued as a drug target, particularly for the treatment of cardiopulmonary diseases. Although thousands of molecules have been reported to inhibit HNE, yet very few are being evaluated in early clinical trials, with sivelestat as the only approved HNE inhibitor. We report here a novel chemotype of sulfonated nonsaccharide heparin mimetics as potent and noncompetitive inhibitors of HNE. Using a chromogenic substrate hydrolysis assay, 14 sulfonated nonsaccharide heparin mimetics were tested for their inhibitory activity against HNE. Only 12 molecules inhibited HNE with IC50 values of 0.22-88.3 μM. The inhibition of HNE by these molecules was salt-dependent. Interestingly, a specific hexa-sulfonated molecule inhibited HNE with an IC50 value of 0.22 μM via noncompetitive mechanism, as demonstrated by Michaelis-Menten kinetics. The hexa-sulfonated derivative demonstrated at least 455-, 221-, 1590-, 21-, and 381-fold selectivity indices over other heparin-binding coagulation proteins including factors IIa, Xa, IXa, XIa, and FXIIIa, respectively. At the highest concentrations tested, the molecule also did not significantly inhibit other serine proteases of plasmin, trypsin, and chymotrypsin. Further supporting its selectivity, the molecule did not show heparin-like effects on clotting times of human plasma. The molecule also did not affect the proliferation of three cell lines at a concentration as high as 10 μM. Interestingly, the hexa-sulfonated molecule also inhibited cathepsin G with an IC50 value of 0.57 μM alluding to a dual anti-inflammatory action. A computational approach was exploited to identify putative binding site(s) for this novel class of HNE inhibitors. Overall, the reported hexa-sulfonated nonsaccharide heparin mimetic serves as a new platform to develop potent, selective, and noncompetitive inhibitors of HNE for therapeutic purposes.

Project description:Mice and diets. One-month-old male mice of the long-lived B6C3F1 strain were purchased from Harlan (Indianapolis, IN) and maintained as described after weaning (15). Mice were housed in groups of 4 per cage and fed a non-purified diet, PMI Nutrition International Product #5001 (Purina Mills, Richmond, IN). At 5 months of age, the mice were individually housed, and randomly assigned to one of two groups, control (CON) or long-term CR (LTCR). CON mice were fed 93 kcal per week of a defined control diet (AIN-93M, Diet No. F05312, BIO-SERV). LTCR mice were fed 52.2 kcal per week of a defined CR diet (AIN-93M 40% Restricted, Diet No. F05314, BIO-SERV). The LTCR mice consumed approximately 40% fewer calories than mice in the CON mice. The CR diet was enriched so that the CR mice consumed approximately the same amount of protein, vitamins, and minerals per gram body weight as the control mice. Experimental design. At 20 months of age, cohorts of mice in the CON group were randomly assigned to one of 7 experimental groups (Fig. 1). A CON group continued to be fed 93 kcal per week of control diet for 8 weeks. A CR8 group was fed 77 kcal per week of CR diet for 2 weeks, followed by 52.2 kcal per week of CR diet for 6 weeks. The remaining dietary groups were fed the control diets containing, respectively, metformin (MET; Sigma, St. Louis, MO), glipizide (GLIP; Sigma), GLIP plus MET (GM), rosiglitazone (ROS; Avandia, SmithKline Beecham) or soy isoflavone extract (SOY; NOVASOY 400, Life Extension Foundation) for 8 weeks at the dosages indicated in Table 1. The drugs were mixed with powdered control diet and cold-pressed into one gram pellets (BIO-SERV Inc.). At 0900, all mice were fed 2/7 of the weekly allotment of food on Monday and Wednesday and 3/7 on Friday. The mice had free access to acidified tap water. They were fasted for 48 hours and killed by cervical dislocation at 22 months of age. No signs of pathology were detected in the animals used for the studies reported (n=4 per group). Organs were removed rapidly, flash frozen, and stored in liquid nitrogen. The weights of the mice were monitored bi-weekly. Mouse weights are given in Table 1. Measurement of specific mRNA levels. Liver total RNA was isolated as described from livers of pathology-free mice in each group (n=4 per group) (13). mRNA levels were measured using Affymetrix mouse U74Av2 arrays according to standard Affymetrix protocols (Affymetrix). Probe set expression measurement and normalization. After hybridization and scanning, raw image files were converted to probe set data (*.CEL files) using Microarray Suite (MAS 5.0). Probe set data from all 32 arrays were simultaneously analyzed with the Robust multichip Average (RMA) method to generate normalized expression measures for each probe set (Fig. 2; Ref. 24) The data were further filtered to exclude probe data sets that were “Absent” across all 32 arrays according to the MAS 5.0 detection algorithm (1,47). Keywords = CR mimetics Keywords = microarray profiling Keywords = drug discovery Keywords = gene-expression biomarkers Keywords: other

Project description:Although bone morphogenetic protein-2 (BMP-2) is known to be the most potent stimulator available for bone formation, a major barrier to widespread clinical use is its inherent instability and absence of an adequate delivery system. Heparin is being widely used in controlled release systems due to its strong binding ability and protective effect for many growth factor proteins. In this work, we developed a hydrogel surface that can mimic heparin to stabilize BMP-2 and to enhance osteogenesis by introducing heparin-mimicking sulfonated molecules such as poly-vinylsulfonic acid (PVSA) or poly-4-styrenesulfonic acid (PSS), into photo-crosslinkable hydrogel. Bioactivity of BMP-2 was well preserved in the presence of polysulfonates during exposure to various therapeutically relevant stressors. The heparin-mimicking sulfonated hydrogels were effective to bind BMP-2 compared to unmodified MeGC hydrogel and significantly enhanced osteogenic differentiation of encapsulated bone marrow stromal cells (BMSCs) without the addition of exogenous BMP-2. The sulfonated hydrogels were effective in delivering exogenous BMP-2 with reduced initial burst and increased BMSCs osteogenesis induced by BMP-2. These findings suggest a novel hydrogel platform for sequestering and stabilizing BMP-2 to enhance osteoinductive activity in bone tissue engineering. STATEMENT OF SIGNIFICANCE:Although bone morphogenetic protein-2 (BMP-2) is believed to be the most potent cytokine for bone regeneration, its clinical applications require supraphysiological BMP dosage due to its intrinsic instability and fast enzymatic degradation, leading to worrisome side effects. This study demonstrates a novel hydrogel platform that mimics a natural protector of BMPs, heparin, to sequester and stabilize BMP-2 for increased osteoinductive signaling. This study will achieve the stabilization of BMPs with prolonged bioactivity by a synthetic heparin mimic that has not been examined previously. Moreover, the heparin mimetic hydrogel surface can augment endogenous BMP activity by sequestering and localizing the cell-produced BMPs. The additional knowledge gained from this study may suggest basis for future development of material-based therapeutics for tissue engineering.

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Heparin Mimetics: Their Therapeutic Potential.

Publications

Heparin Mimetics: Their Therapeutic Potential.

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