Fibrinogen: biochemistry, epidemiology and determinants

Activation of gelatinases by fibrin is PA/plasmin system-dependent in human glomerular endothelial cells

Evidence suggests that fibrin deposit is related to severity of glomerulonephropathy. Fibrin is considered to play an active role beyond a haemostatic plug or temporary matrix in response to injury. We have reported that fibrin induced specific morphological changes and up-regulated intercellular adhesion molecule-1 expression of glomerular endothelial cells (GECs). Changes of gelatinases activity have been implicated playing a prominent role in glomerular diseases involving matrix turnover. This study examined whether overlying fibrin influences the expression of gelatinase A and B in cultured human GECs and mechanism underlying the activation. No gelatinase activity was detectable in supernatant of cultured GECs; however, physiological concentration of fibrin (0.5-2.0 mg/ml) induced a dramatic expression of activated MMP-2 and MMP-9 at both mRNA and protein level in a dose and time dependent manner. Increased mRNA level of membrane-type 1 matrix metalloproteinases (MT1-MMPs) was also found. Interestingly, we observed that fibrin also induced the expression of tissue type plasminogen activator (tPA), urokinase type plasminogen activator (uPA) and plasminogen activator inhibitor-1 by casein zymographic and reverse zymographic analysis. Fibrin plate assay revealed the net activity was PA predominant. Serine protease inhibitor aprotinin blocked the conversion of pro-gelatinase A and B to their active forms. The results demonstrate that overlying fibrin increased the secretion of gelatinase A and B from GECs. PA/plasmin proteolytic pathways contributed to the activation of gelatinases.

Virchow’s Triad Revisited: Blood Constituents

An update of Virchow's triad for thrombogenesis can be considered by reference to abnormalities in the endothelium/endocardium ('abnormal vessel wall'), abnormalities of haemorhelogy and turbulence at bifurcations,atheroma at vessel wall ('abnormal bloodflow') and abnormalities in platelet as well as the coagulation and fibrinolytic pathways ('abnormal blood constituents'). The constituents of the blood are many and varied, but soluble coagulation factors (such as fibrinogen and tissue factor) and cells (such as platelets)are clearly important. Clearly, 'a continuum exists between health, 'statistically' increased haemostatic abnormalities in prothrombotic or hypercoagulable states and 'overtly' increased clotting in acute thrombosis.Thus, the patients with the highest levels of the markers appear to be the highest risk of disease progression,and if so, a panel of 'high risk' blood constituent indices (platelet and coagulation markers) may potentially give a composite score of risk, and may be a useful tool in predicting subjects at highest risk. Further longitudinal studies are clearly required. There is no doubt that Virchow would be impressed on how his classical triad has expanded to encompass the wide range of pathophysiological processes leading to thrombogenesis.

Thrombogenesis, atherogenesis and angiogenesis in vascular disease: a new 'vascular triad'

Amongst the components of the pathophysiology of atherosclerosis are the tendency to thrombus formation (i.e., thrombogenesis) and the loss of endothelial cell integrity. The endothelium is also implicated in atherogenesis, as vasa vasorum are present in the adventitia and media at a higher density in atherosclerotic tissue, and that neovascularisation leading to collateral growth bypassing obstruction and/or stenoses provides important alternative routes to feeding distal tissues. The development of these new blood vessels is the process of angiogenesis. The present 'viewpoint' article will explore the relationships between the three processes. There is considerable evidence that atherogenesis and thrombogenesis are intimately linked, but angiogenesis in cardiovascular disease is a recently developed concept. We propose a new 'vascular triad' of these abnormal pathophysiological processes, leading to an alternative view of the pathogenesis of vascular disease. Indeed, we suggest that angiogenesis is an important aspect of the pathophysiology of cardiovascular disease, impacting with both thrombogenesis and atherogenesis, in a new vascular triad (the 'Birmingham vascular triad').