346 Brain Research, 597 (1992) 346-349 <Cll992 Elsevier Scienc:e Publishers B.V. All rights reseJVed 0006-8993/92/$05.00 BRES 25454 Comparison of stimulated tissue factor expression by brain microvascular endothelial cells from normotensive ( WKY) and hypertensive (SHR) rats David A. Doron a,b, Richard M. McCarron c, Eliahu Heldman a.b, Anna-Leena Siren a, Maria Spatz c, Giora Feuerstein d, Harvey B. Pollard b and John M. Hallenheck a,c a Department of Neurology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799 (USA), ,. Labaratory ofC:ell Biology and Genetics, Nationalinstitute of Diabetes, Digestil·e, and Kidney Diseases, N/H, Betlresda, MD 20892 (USA), Strake Branch, Nationalinstitute of Neurological Disorders and Stroke, N/H, Bethesda, MD 20892 (USA) and d Department of Pharmacology, SmithK.line Beecham Laboratories, Kingof Prussia, PA /9406-0939 (USA) (Accepted 8 September 1992) Key words: Endotl:lelium; Thromboplastin; Lipopolysaccharide The amounts of tissue factor (TF) expressed by brain microvascular endothelial cells (BMECs) from normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were compared after stimulating the cells with different doses of lipopolysaccharide (LPS), thrombin, phorbol myristic acid (PMA), Ca 2 +·ionophore (A23187), or tumor necrosis factor (TNF) and interleukin·l (IL.l). Treatment ofcultured BMECs fron. WKY and SHR with all of these factors dose·dependently increased their total amount of TF; no substantive differences in the Ieveis of enhanced TF expression were observed between WKY and SHR BMECs. We conclude that stimulated endothelium from rats with hypertension, a major stroke risk factor, is not hyperresponsive with respect to TF expression when compared to normotensive controls. We have previously reported that rats with risk factors for stroke such as hypertension, advanced age and diabetes, develop mare strake events than contral rats when the animals are challenged with a single dose of lipopolysaccharide (LPS) 10 • Differences in response to a provocative dose of LPS in vivo between rats with and without risk factors for strake may depend an the degree of prothrambotic transfarmation which ulti- mately occurs in lacal endothelium 4 - 6 • This local trans- farmation could be pramoted by the risk factor indi- rectly through accumulation of perivascular macro- phages that release cytokines such as tumor necrosis factor-a (TNF-a) and interleukin-1 (IL-1 ). These cy- tokines render endothelium procoagulant 4 • 5 • 7 and in- crease cellular adhesion 26 • Another possibility is that the sensitivity to different endothelial cell (EC) activa- tors of hemostasis such as IL·l, TNF-a and LPS has been enhanced by the risk factor acting directly on the endothelium. lt would be consistent with the latter possibility if the response of brain EC from hyperten- sivt; rats to LPS, IL·l and TNF-a were to be an enhanced expression of tissue factor (TF) compared to that of brain ECs from normotensive rats. TF is a SO kDa phospholipid-protein complex that triggers blood coagulation in association with factor VII via the extrinsic pathway 22 • lt is known to be constitutively synthesized by a variety of cells including fibroblasts 15 • 16 , macrophages 2 • 23 , smooth muscle cells 15 • 16 and EC 6 • 14 • 16 • 21 • In addition, numerous studies have shown that LPS 6 • 14 .2 1 , TNF-a 3 • 7 • 24 , and IL-13.2s, increase TF synthesis and expression in a variety of cells in culture. In the present paper, we tested the hypothesis that the differences in stroke events between normotensive and hypertensive rats obseiVed after LPS treatment in vivo 11 may in part be due to differences (as a result of the hypertension) in the reactivity of their brain ECs to prothrombotic mediators such as LPS, IL-1 and TNF-a. Therefore, we have compared the effects of these factors on TF expression by brain microvascular EC Co"espondenct: J. Hallenbeck, Stroke Branch, NlNDS, NIH, Bldg 36, Room 4004, Bethesda, MD 20892, USA.