fibrin and Iron-Overload

Topics: Cell Adhesion Molecules; Fibrin; Humans; Iron; Iron Overload; Macrophages; Matrix Metalloproteinases; Multiple Sclerosis; Vasculitis

The activation of blood coagulation leads to the formation of thrombin that, in turn, converts soluble plasma fibrinogen into insoluble fibrin clot. In healthy individuals, fibrin is effectively degraded; however, in prothrombotic states, proteolysis of fibrin clots are often delayed or even inhibited, and is associated with altered fibrin structure. We have previously shown that in inflammatory conditions like stroke and diabetes, this fibrin forms dense matted deposits. Although there are several factors that modify fibrin structure and delay fibrinolysis in these conditions, no mechanism is yet known to be responsible for a persistent presence of thrombi in the coronary and/or cerebral circulations. It seems, therefore, desirable to better understand this phenomenon in order to improve the effectiveness of thrombolytic therapies. Here, we show that ferric ions can activate non-enzymatic blood coagulation resulting in the formation of fibrin-like dense matted deposits (DMD) demonstrable by electron scanning microscopy (SEM). These DMDs are similar to those found in stroke and diabetes. On the basis of these findings we can conclude that the spontaneous formation of fibrin-like dense deposits in patients' blood may be a consequence of what is known as iron overload. Therefore, it is possible that inactivation of unbound iron in blood by small molecular weight chelating agents may prevent thrombotic consequences of the excessive accumulation of iron in the circulation.

Topics: Blood Coagulation; Diabetes Mellitus; Female; Ferric Compounds; Fibrin; Humans; Iron Chelating Agents; Iron Overload; Male; Stroke; Thrombin; Thrombosis

Fibrinogen (FBG) is a high-molecular-weight protein and precursor to the enzymatically formed fibrin. It has been recently discovered that FBG can be converted into an insoluble, fibrin-like polymer by a nonenzymatic action of hydroxyl radicals (HRs). These free radicals are generated due to the reaction between hydroxyl groups of water and trivalent ferric ions without the participation of any redox agent. The interaction between HRs and FBG occurs in a purified system, as well as in human plasma and in whole blood. Scanning electron microscopy (SEM) of thrombin-induced fibers and those generated with ferric chloride has shown substantial differences in their morphology and susceptibility to enzymatic degradation. Fibrin strands caused by thrombin are thick and easily digested with chymotrypsin. By contrast, the dense matted deposits formed from FBG in the presence of ferric ions are remarkably resistant to proteolytic and chemical degradations due to the presence of intermolecular hydrophobic bonds. Thus, we postulate that this iron-catalyzed reaction represents a novel blood coagulation pathway operating in degenerative diseases. By means of SEM, we showed the presence of dense fibrin-like deposits in the blood of diabetic patients. Therefore, the prothrombotic state and cardiovascular complications observed in diabetes can be explained in terms of the persistent in vivo action of free iron. This phenomenon may explain hemorheologic disturbances in patients with metabolic syndrome and other diseases caused by iron overload. Of note, HRs can be effectively scavenged by phenolic substances; therefore, certain natural polyphenolic substances, which also scavenge HRs, may be considered to have a potential antidiabetic effect. Moreover, natural or synthetic iron-binding substances may also be considered as a new class of antidiabetic drugs.

Topics: Blood Coagulation; Diabetes Complications; Diabetes Mellitus; Fibrin; Fibrinogen; Humans; Iron; Iron Overload