The antiphospholipid syndrome is characterized by the presence of anti-ß2-GPI antibodies that induce the activation of a signaling pathway leading to the expression of Tissue factor (TF), the major initiator of the clotting cascade in human platelets, monocytes and endothelial cells. Heparanase is an endo-beta-D-glucuronidase capable of cleaving heparan sulfate side chains at a low pH. Recent papers have shown that heparanase is directly involved in the activation of the coagulation system. Heparanase was demonstrated to interact with TF and enhance the generation of factor Xa.
In the present study we will investigate the role of heparanase in the pathogenesis of Antiphospholipid Syndrome (APS), implementing a rational drug design approach to discover and develop new symmetrical 2-aminophenyl-benzazolyl-5-acetate derivative (RDS3337), able to inhibit Heparanase activity.
Thus, this research project is developed in 3 main objectives:
1. Analysis of the role of heparanase in the signal transduction pathway triggered by anti-beta2-GPI antibodies;
2. Evaluation of the effect of heparanase inhibitors on tissue factor expression and release. All the compounds will be previously tested for selectivity, efficacy and safety;
3. Analysis of heparanase activity in plasma of APS patients and relationship with clinical features and active arterial thrombosis.
Research in this field may contribute to clarify whether pharmacological regulation of heparanase might modify the disease activity, thus disclosing new potential therapeutic targets for APS.
Heparanase activity is implicated in neovascularization, inflammation and autoimmunity. Heparanase expression is enhanced in the patients with Crohn¿s disease and ulcerative colitis and in the synovial fluid and tissue of patients with rheumatoid arthritis. It has also been implicated in the severity of atherosclerosis, since its expression is upregulated in vulnerable coronary plaques. This enzyme can play a role as inflammatory mediator, modifying and destroying endothelial surface layer structure, leading to the impairment of endothelial functions, promoting progression of vascular diseases.37 Moreover, Heparanase induces the transcription of pro-angiogenic, pro-thrombotic and pro-inflammatory factors, promoting the release of pro-inflammatory cytokines from human peripheral blood mononuclear cells and generating soluble HS fragments that activate TLR-dependent pathway(s). In fact, cytokine induction by Heparanase appears to involve TLR-2, TLR-4, and NF-B. The involvement of the enzyme in inflammatory reactions was further supported by anti-inflammatory effects demonstrated for Heparanase-inhibiting substances (i.e., heparin, synthetic heparin-mimicking compounds) in animal and clinical studies. Thus, therapeutic benefits are expected in inflammation by pharmacological strategies that target Heparanase, reducing heterotypic interactions between epithelial, endothelial, and immune cells due to the enzyme involvement.
Heparanase upregulates the expression of TF and interacts with the Tissue factor pathway inhibitor (TFPI) on the cell surface membrane of endothelial cells, leading to dissociation of TFPI and increasing coagulation activity. It was also demonstrated that Heparanase over-expressing mice generated a larger thrombus within a shorter period of time compared to control mice, suggesting the procoagulant effect of Heparanase. In conclusion, new synthesized Heparanase inhibitor (RDS3337) could be able to prevent the main signal transduction pathway triggered by anti-ß2-GPI antibodies in endothelial cells and platelets introducing a new task in the pharmacological approach of APS. In addition, Heparanase activity detection may be useful in monitoring patients and evaluating the risk stratification. Further studies are in progress to test the levels of Heparanase activity in APS patients and their relationship with disease progression.