Effects of increased blood content of fibrinogen on mouse pial vessels in vivo

Abstract

Fibrinogen (Fg) is a biomarker of inflammation for many cardiovascular and cerebrovascular diseases that are commonly associated with vascular dysfunction. We tested the hypothesis that at pathologically high levels Fg increases endothelial cell (EC) layer permeability through generation of reactive oxygen species (ROS) and activation of matrix metaloproteinases (MMPs). Fg (a total blood content of 4 mg/ml) or similar volume of phosphate buffered saline (PBS) was infused to male wild-type (WT, C57BL/6J) or MMP-9 gene knockout (MMP9−/−) mice. Pial venular leakage of fluorescein isothiocyanate-labeled bovine serum albumin to Fg or PBS alone and to topically applied histamine (10−5 M) were assessed. Production of ROS in response to topical application of pyocyanin (1 μM) was assessed by measuring the fluorescence of a ROS detecting reagent 2′,7′-Dichlorofluorescein diacetate. Intravital fluorescence microscopy and off-line image analysis were used for observation and assessment of venular permeability and ROS formation. Pial venular leakage and ROS formation were greater in presence of Fg than in control group and were more in WT mice compared to MMP9−/− mice. These data indicate that Fg compromises vascular integrity by enhanced formation of ROS and can be mediated through activation of MMPs. Our findings show that elevated blood level of Fg may play a significant role in vascular dysfunction and remodeling.