Regulation Activity of Heparin in Complement System

Abstract

Heparin (HP) can bind to a variety of proteins, including growth factors, pro-inflammatory chemokines and cytokines, extracellular matrix proteins, and complement proteins. HP has a variety of biological activities, many of which are of interest because of their potential therapeutic utility. By regulating the activity of HP-binding proteins, HP and the related glycosaminoglycan (GAG), heparan sulfate (HS), can influence various biological processes giving HP therapeutic applications as an antithrombotic, antiatherosclerotic, anticomplement, antiinfective, anticancer, and anti-inflammatory agent. Monosaccharide and disaccharides with structural similarities to dextran did not cause a detectable decrease in C3b-factor H binding, while sugar polymers caused large decreases in the affinity between C3b and factor H as a result of the polysaccharide occupying the binding site in C3b or in factor H, preventing their interaction. HP and the structurally similar HS regulate multiple steps in the complement system including ones in both the classical and alternative pathways. Quantitative data in the form of association rates, dissociation rates, and affinity constants for complex formation are provided for many of these interactions.