EXPERIMENTAL STUDIES Overexpression of Cyclooxygenase-2 in Rabbit Basilar Artery Endothelial Cells after Subarachnoid Hemorrhage Yves R. Tran Dinh, M.D., Ph.D., Anas Jomaa, M.D., Jacques Callebert, Ph.D., Anne-Marie Reynier—Rebuffel, Ph.D., Alain Tedgui, Ph.D., Adrien Savarit, B.Sc., Richard Sercombe, Ph.D. Centre National de la Recherche Scientifique UPR 646, IFR6, Université Paris 7, (YRTD, AJ, AMRR, AS, RS); Centre de Recherche Claude Bernard and Service de Biochimie et Biologie Moléculaire, Hôpital Lariboisière, IFR6 (JC); and Institut National de la Santé et de la Recherche Médicale, Unité 541, IFR6 (AT), Paris, France OBIECTIVE: We investigated the expression in rabbit basilar arteries of cyclooxygenase (COX)-2, which is the inducible isoform of the enzyme of prostaglandin (PG) production, and the concentrations of the proinflamma- tory cytokine tumor necrosis factor a (TNFa) and representative PGs in the cerebrospinal fluid (CSF) after expérimental subarachnoid hemorrhage (SAH). METHODS: Seven sets of basilar arteries were removed from control rabbits and from rabbits killed 1 and 3 days after induced SAH. The arteries were subjected t0 identical simultaneous immunolabeling for examination with a confocal microscope. One-half of each artery was stained for the constitutive form COX-1 and the other half for COX-2. CSF was sampled in control animals and at 6 hours, 1 day, and 3 days for assays of TNFa, PGEz, and 6-keto-PGF1 (métabolite of PGI2). RESULTS: COX-1 immunoreactivity in the endothelial layer was similar in the three groups. Weak endothelial COX-2 immunoreactivity was found in arteries of control animals. COX-2 staining was higher in the group killed at 3 days compared with the control group (P < 0.05). The levels of PGE2 and 6-keto-PGF1O, in the CSF peaked significantly at 6 hours, then decreased at 3 days t0 the basal Ievel (PGE2) or significantly lower (6-keto-PGF1). TNFa was undetectable in control CSF, significantly higher (P < 0.001) at 6 hours, and undetectable at 3 days. CONCLUSION: After SAH, endothelial COX-1 immunoreactivity does not change, whereas overexpression of COX-2 occurs at 3 days. This induction does not seem linked t0 TNFa production, nor is it responsible for early raised levels of PGE2 and PGI2 in the CSF. We suggest that the role of induced COX-2 may be t0 modify gene expression and hence alter the properties of the vessel wall after SAH. (Neurosurgery 48:626—635, 2001) Key words: Cyclooxygenase-Z, Prostacyclin, Prostaglandin E2, Rabbits, Subarachnoid hemorrhage, Tumor necrosis factor a the extraluminal aspect of cerebral arteries, such as occurs during subarachnoid hemorrhage (SAH), is highly pathogenic for the three layers of the arterial wall: the adventitia with its perivascular nerves, the smooth muscle layer of the media, and the endothelial cells of the intima. In a large proportion of patients, SAH is complicated Within less than 1 week by a substantial, prolonged narrowing of the cerebral arteries. This phenomenon has stimulated many dif- ferent studies of cerebral artery states. In an in Vitro study, we deterrnined that functional changes related to cyclooxygenase Close, sustained contact between blood constituents and 626 (COX) metabolites occur in rabbit basilar arteries 3 days after SAH (40). For example, although the SAH group relaxed normally to acetylcholine in control Krebs buffer, the presence of oxyhemoglobin in the bath dramatically reduced the relax- ation, which also was the case in arteries from non-SAH rabbits that were pretreated with indomethacin. We inter- preted these results as demonstrating reduced release by ace— tylcholine of prostacyclin (PGIZ) and/ or increased release of constrictory prostaglandins (PGs). This study could not indi- cate whether such changes depended on modified COX ac- tivity or expression. Neurosurgery, Vol. 48, No. 3, March 2007