Endothelial cell expression of tissue factor in sickle mice is augmented by hypoxia/reoxygenation and inhibited by lovastatin

Abstract

Abnormal tissue factor (TF) expression has been demonstrated on blood monocytes and circulating endothelial cells in humans with sickle cell anemia. We have now studied sickle transgenic mice to help define the biology of endothelial TF expression in sickle disease. Using immunostaining of tissue sections, we find that this is confined almost exclusively to the pulmonary veins. About 15% and 13% of these exhibit TF-positive endothelium in the wild-type normal mouse and the normal human hemoglobin (HbA)-expressing control transgenic mouse, respectively. The mild sickle mouse is indistinguishable from normal (ϳ 14% positive), but TF expression is significantly elevated in the moderate and severe mouse models of sickle disease (ϳ 29% and ϳ 41% positive, respectively). Exposure of the mild sickle mouse to hypoxia for 3 hours, followed by reoxygenation, converted its TF ex

Endothelial nitric oxide synthase and nitric oxide regulate endothelial tissue factor expression in vivo in the sickle transgenic mouse

“…Thus, the relevant effect of H/R on triggering TF expression is exerted early after cessation of hypoxia, in the first few hours of the reoxygenation period, consistent with our previous observations of many other parameters post-H/R [4,5,6], even though maximal expression of actual TF protein requires many hours longer [3]. These results suggest not only that NO may be of therapeutic benefit but also that endogenous NO could be a regulator of TF expression, as influenced by inflammation.…”

“…The nature of these mice and the methods used to genotype them have been described [3]. We previously found that this hBERK1 mouse is very similar to the most-severe BERK mouse in having high TF expression even at ambient air without H/R [3].…”

“…This study examines our hypothesis that the enhanced endothelial TF expression evident in the sickle transgenic mouse [3] is modulated by endogenous NO produced by eNOS. Elsewhere, we have unambiguously demonstrated that this TF expression mouse is triggered by the inflammatory state that is known to develop in the NY1DD mouse on exposure to H/R [6].…”

“…We measured expression of TF by the pulmonary vein endothelium exactly as we previously described [3], using immunofluorescence microscopic review of tissue sections triple stained for nuclei and endothelial marker CD31 and murine TF, with fluorescein isothiocyanate and tetramethylrhodamine-5(and6)-isothiocyanate-labeled secondary antibodies. For this, we used the partially purified polyclonal antibody preparation to murine TF [36] that we previously described [3]. Quality control measures and negative controls were as previously detailed [3].…”

“…The mixed background sickle mice (S1SAntilles, hBERK, and BERK models) all exhibit this anomaly even at ambient air, whereas their appropriate same strain HbA-BERK control does not [3]. Remarkably, the mild-phenotype NY1DD sickle mouse, which at ambient air is identical to normal control mice in having low-TF expression, develops a phenotype switch to an increased TF expression if exposed to transient hypoxia/reoxygenation (H/R), which has no such effect on the normal control mouse.…”