Increasing evidence suggests that most cardiovascular diseases are associated with inflammation, which consists of a cascade of events leading to major changes in the microcirculation. I hypothesize that enhanced proteolytic activity in the SHR (Spontaneously Hypertensive Rat) may cause cell membrane receptor cleavage and I examine this for the glycocalyx of RBC (Red Blood Cells). I focus my research on MMPs (Matrix MetalloProteinases), and more precisely on the MMP-2, MMP-7 and MMP-9, whose activity in the SHR is more elevated than in the control WKY (Wistar-KYoto) rat.

After a brief introduction of current publications on RBC aggregation and selected aspects of hypertension, I demonstrate that MMPs cleave the inner core of RBC glycoproteins. For this purpose, I treat WKY blood with MMPs and observe a strong stimulation of dextran-induced aggregation, which indicates RBC membrane alteration. I test other types of proteases and amylases and demonstrate that MMPs prevent fibrinogen-induced aggregation by cleaving the associated receptor located on the RBC membrane. I quantify the RBC aggregation by using two different methods: first, I apply different shear stresses to the rouleaux and determine their size as a measure for RBC aggregation strength; secondly, I label the glycocalyx with a fluorescent lectin. I also study the impact of MMP concentration and treatment time on RBC aggregation. Finally, I examine the role of MMPs in the process of ageing by comparing SHR old and young RBC tendency to form aggregates. I mix SHR plasma and WKY RBC and show that the proteases responsible for RBC glycocalyx cleavage derive from the SHR plasma and that they can be inactivated by MMP inhibitors. These results indicate that RBC aggregation and ageing may indeed be mediated by glycocalyx cleavage induced by MMPs present in SHR