Pericytes of the brain microvasculature express γ‐glutamyl transpeptidase

Abstract

The expression of y-glutamyl transpeptidase (GGT) is a specific property of the brain capillary endothelium that constitutes the blood-brain barrier. We report here the detection of GGT, not only in endothelial cells, but also in pericytes, demonstrating that a brain capillary-specific pericyte population exists. We raised antibodies to GGT using a porcine brain microvessel GGT -protein-A (staphylococcal protein A) fusion protein as antigen which was expressed in Escherichia coli. The immunohistochemical analysis of the subcapillary distribution of GGT in porcine brain cortex and cerebellum sections by both light and electron microscopy revealed the expression of GGT in the capillary-adjacent pericytes in addition to the GGT-positive endothelial layer. We confirmed these data for cultured porcine brain microvascular endothelial cells and pericytes. GGT immunofluorescence could be detected in both cell types in culture. Endothelial cells exhibited a weak staining, whereas pericytes were strongly positive for GGT. Due to the high phagocytotic activity of pericytes and their location on the abluminal surface of the microvessels, we propose a possible protective or detoxifying function of GGT in cerebrovascular pericytes.

Transport and Detoxication: Principles, Approaches, and Perspectives for Research on the Blood – Brain Barrier

“…In contrast, immunochemical, histochemical, and biochemical studies by Frey et al [15] and by Risau et a1. ['61 establish that the greatest GGT activity in brain capillaries is in the abluminally situated pericytes and not in the endothelial cells.…”

Can .GAMMA.-Glutamyltransferase be an Additional Marker of Arterial Stiffness?

“…As a potential mechanism it has been proposed that GGT reduces Fe 3+ to its bivalent form and releases a free thyil radical, which oxidizes LDL in the extracellular space. 3,5,16 Although the exact mechanism has not been fully elucidated, GGT levels appeared to be an independent risk factor for the development of cardiovascular disease, hypertension, stroke, and type 2 DM, and their complications, in several prospective cohort studies after adjusting for alcohol consumption. [17][18][19][20] From the viewpoint of GGT level in our results, serum triglycerides had an influence on serum GGT level in both genders.…”

γ-Glutamyltransferase as a Risk Factor for Cardiovascular Disease Mortality

“…8,24 Recent studies have demonstrated that GGT is expressed not only in the liver and kidney but also in the cerebrovascular endothelium, the pericytes, and most other cell types. 26 Therefore, GGT activity can be used as a biochemical marker for the blood-brain barrier. 27 This might explain the predictive value of GGT in fatal cerebrovascular events, because GGT is released by impaired cerebral endothelial cells in the formation of atherosclerotic plaques.…”