Endotoxin-induced procoagulant activity in equine peripheral blood monocytes.

This study examines the activation of clotting factors in horse blood cells, specifically monocytes, by endotoxins that could potentially contribute to blood clotting disorders after conditions of reduced blood supply and endotoxemia in these animals. The cells, when exposed to Escherichia coli endotoxin, showed significantly increased procoagulant activity, initiating within a couple of hours of exposure, peaking about 6 hours in, and then gradually declining.

Introduction

• The researchers were interested in the role monocyte procoagulant activity (PCA) plays in the formation of coagulopathies – disorders that affect the blood’s ability to clot – in different diseases.
• The focus was on the equine species, particularly because endotoxin-triggered coagulopathies are common after intestinal ischemia and endotoxemia – conditions characterized, respectively, by inadequate blood supply to the intestines and the presence of endotoxins in the blood.

Methodology and Experiments

• The team worked with monocytes isolated from the blood of five healthy adult horses.
• These cells were exposed to Escherichia coli endotoxin in the laboratory.
• The PCA was gauged by how much cellular lysate (the fluid containing dissolved or suspended components of cells) could speed up equine plasma clotting times in a modified recalcification assay (a test measuring the blood’s ability to form clots).
• They determined the source of PCA to be thromboplastin due to the absence of clot formation in factor VII-deficient plasma.
• They found that PCA induction happened as early as 2 hours following endotoxin exposure, with a peak at 6 hours and then a gradual decrease.
• They also found out that the amount of PCA correlated with the concentration of endotoxin and the count of monocytes.

Other Findings

• In other cells’ tests, neither platelets nor neutrophils yielded PCA, irrespective of endotoxin presence or absence.
• At a concentration, lymphocytes did produce a significant PCA quantity, compared to the time-matched controls.
• When monocytes were incubated with either neutrophils or lymphocytes, pregnancy did not change the PCA measurement.
• In contrast, when monocytes and platelets were co-incubated, there was a significant increase in PCA, with further enhancement in the presence of the endotoxin.