Sodium salicylate inhibits prostaglandin formation without affecting the induction of cyclooxygenase-2 by bacterial lipopolysaccharide in vivo. (73/645)

The mechanisms underlying the anti-inflammatory properties of salicylate are not well understood. In particular, while salicylate inhibits prostaglandin production in vivo it only weakly inhibits cyclooxygenase (COX)-1 or -2 activity in vitro. Thus, it has often been suggested that in vivo salicylate may inhibit the expression rather than the activity of COX, particularly COX-2. Using a model of acute COX-2 expression in the rat, we show that salicylate inhibits COX-2 activity in vivo without affecting COX-2 expression. In anesthetized rats LPS (6 mg kg(-1), i.p.) increased the expression of COX-2 as evidenced by increased circulating levels of 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha), a stable breakdown product of PGI(2)), greatly exaggerated formation of 6-keto-PGF(1alpha) following arachidonic acid (AA) challenge (3 mg kg(-1), i.v.), and increased expression of COX-2, but not COX-1, protein. Diclofenac (3 mg kg(-1), i.p.) or the COX-2 selective agent diisopropyl fluorophosphate (10 mg kg(-1), i.p.) decreased the LPS-induced increase in circulating 6-keto-PGF(1alpha) and the exaggerated 6-keto-PGF(1alpha) production following AA challenge. Sodium salicylate (20 or 120 mg kg(-1), i.p.) (administered either 1 h prior, or once per day for 3 days prior, to LPS injection) reduced only the LPS-induced increase in circulating 6-keto-PGF(1alpha), but not the exaggerated 6-keto-PGF(1alpha) production following AA challenge or the expression of COX-2. Thus, salicylate inhibits LPS-induced COX-2 activity in a manner that is overcome by provision of excess substrate and independent of effects on COX-2 expression. In conclusion, our results exclude mechanisms other than direct enzyme inhibition as responsible for the anti-COX effects of salicylate.  (+info)

Role of calcitonin gene-related peptide in prostaglandins-mediated ischemic preconditioning in guinea pig hearts. (74/645)

AIM: To examine the role of calcitonin gene-related peptide (CGRP) in ischemic preconditioning induced by prostaglandins in isolated guinea pig hearts. METHODS: The isolated guinea pig hearts were perfused in a Langendorff model. The heart rate, coronary flow, left ventricular pressure, and its first derivatives (+/-dp/dt(max)) were recorded and the calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) and 6-keto-PGF(1 alpha) were measured. RESULTS: Endothelin-1 (200 pmol in 1 mL K-H buffer) reduced the left ventricular developed pressure and its first derivatives (+/-dp/dt(max)), heart rate, and coronary flow. Preconditioning with two cycles of 5-min global ischemia and 5-min reperfusion attenuated endothelin-1 induced myocardial injury, and concentrations of both CGRP and 6-keto-PGF(1alpha) in the coronary effluent were markedly raised in the preconditioning periods. Pretreatment with capsaicin, which depletes endogenous CGRP, abolished the elevated level of CGRP concomitantly with loss of the cardioprotection induced by ischemic preconditioning. CGRP(8-37) (100 nmol/L), a selective CGRP1 receptor antagonist, also abolished the protective effects of ischemic preconditioning. After pretreatment with indometacin (10 micromol/L), an inhibitor of cyclooxygenase, the protective effects of ischemic preconditioning were abolished and the release of 6-keto-PGF1alpha was no longer elevated. Pretreatment with indometacin abolished the elevated level of CGRP in the coronary effluent. CONCLUSION: Endogenous prostaglandins are involved in the protective effects of ischemic preconditioning, and the beneficial effects of prostaglandins are mediated by CGRP in the guinea pig heart.  (+info)

Effect of dietary polyunsaturated fatty acids on uterine prostaglandin synthesis in the cow. (75/645)

Dietary polyunsaturated fatty acid (PUFA) intake in humans can affect the incidence of a variety of diseases including coronary heart disease. Feeding high PUFA diets to cows can alter the PUFA content of milk for human consumption. PUFAs supply the precursors for prostaglandin (PG) synthesis and PGs in turn influence many aspects of reproduction. This study examined the effects of a control (CONT), a high n-6 PUFA diet (derived from protected soya) and a high n-3 diet (derived from protected linseed) on uterine PG synthesis in the lactating dairy cow. Endometrial explants obtained on days 15-17 of the oestrous cycle were cultured for an initial 42 h in vitro in fully defined medium (basal production) and then challenged with control medium, oxytocin (OT; 20 or 200 nM) or calcium ionophore A23187 (CaI; 10 microM). PGF(2 alpha), PGE(2) and 6-keto-PGF(1 alpha) were measured in the spent medium. The experiments were repeated using tissue from two groups of cows, nine in Experiment 1 (three cows per diet) and seven in Experiment 2 (four CONT and three n-6). Results of the two experiments were consistent. The basal concentrations of all three PGs were significantly lower (>50% reduction) in the n-6-fed group in comparison with CONT and n-3 groups. The n-3 diet did not alter basal PGF(2 alpha) and PGE(2) but increased 6-keto-PGF(1 alpha). The n-6 diet also inhibited the ability of the tissue to respond to both OT and CaI, with significant reductions in the stimulated levels of all three PGs. In contrast, the n-3 diet only had minor effects; it did not alter the response to OT but did reduce the long-term response to CaI at 24 h post treatment. In conclusion, dietary PUFA intake can inhibit PG production in bovine endometrial explants, with a more pronounced effect following n-6 rather than n-3 supplementation. These data suggest that a high n-6 diet reduces the endometrial capacity to produce PGs and may therefore have implications for the control of luteolysis and other PG-mediated events such as ovulation.  (+info)

Antithrombin III prevents early pulmonary dysfunction after lung transplantation in the dog. (76/645)

BACKGROUND: Ischemia-reperfusion injury with the resulting inflammatory response is a devastating complication of lung transplantation; much of the tissue damage could be diminished by control of the inflammatory response. Recent studies have show that antithrombin III (AT III) has an anti-inflammatory effect in addition to its established role in the regulation of blood coagulation. Thus, we hypothesized that the administration of AT III might help to prevent ischemia-reperfusion injury after lung transplantation. METHODS AND RESULTS: The study was performed in a dog model of orthotopic lung transplantation. Dogs were randomly assigned to receive either vehicle (controls) or AT III. We observed that in control dogs, during the 180-minute period after lung transplantation, the arterial O(2) partial pressure decreased and both the alveolar-arterial O(2) difference and the pulmonary vascular resistance increased. By contrast, these parameters remained unchanged in the group of dogs receiving AT III. Dogs with transplants receiving AT III did not show an increase in cell adhesion molecules, and histological examination revealed almost an absence of inflammatory response. The administration of AT III produced a marked increase in serum prostacyclin (PGI(2)) levels, whereas in control dogs, the PGI(2) levels did not change. The beneficial effect of AT III was not observed when dogs received indomethacin to prevent the stimulation of PGI(2) release by AT III. CONCLUSIONS: Our results demonstrate that AT III prevents ischemia-reperfusion injury in a dog model of lung transplantation and that this effect is conditioned by an increase in PGI(2) production.  (+info)

Regulation of cyclooxygenase by the heme-heme oxygenase system in microvessel endothelial cells. (77/645)

Heme oxygenase (HO) is a microsomal enzyme that oxidatively cleaves heme to form biliverdin, with the release of iron and carbon monoxide (CO). HO not only controls the availability of heme for the synthesis of heme proteins but also is responsible for the generation of CO, which binds to the heme moiety of heme proteins thus affecting their enzymatic activity. Cyclooxygenase (COX) is a heme protein that catalyzes the conversion of arachidonic acid to prostaglandin H(2), the precursor of prostanoids that participate in the regulation of vascular function. The goal of the present study was to determine whether the heme-HO system regulates COX enzyme expression and activity in vascular endothelial cells. Endothelial cells stably transfected with the human HO-1 gene exhibited a severalfold increase in human HO-1 mRNA levels, which was accompanied by an increase in HO activity and a marked decrease in prostaglandin (PG) E(2) and 6-keto-PGF(1alpha) levels. Exposure of cells to CoCl(2), an inducer of HO-1 gene expression, resulted in increases in HO-1 protein levels and HO activity. The increase in HO activity was associated with a subsequent decrease in COX activity, which returned to normal levels following normalization of HO activity. The addition of heme resulted in an increase in COX activity with an increase in PGE(2) and 6-keto-PGF(1alpha) levels. The degree of HO-1 expression and, consequently, the level of cellular heme, were directly related to COX activity. These results demonstrate that the heme-HO system can function as a cellular regulator of the expression of vascular COX, thus influencing the generation of prostanoids, PGE(2) and PGI(2), known to play a role in vascular homeostasis.  (+info)

Oral eicosapentaenoic acid for complications of bone marrow transplantation. (78/645)

The 'systemic inflammatory response syndrome' (SIRS) may represent the underlying cause of complications after bone marrow transplantation (BMT). This study was conducted to determine whether blocking the etiologic factors of SIRS could improve the complications of BMT. Sixteen consecutive patients with unrelated donors were allocated alternately to two groups. Seven patients received 1.8 g/day of eicosapentaenoic acid (EPA) orally from 3 weeks before to about 180 days after transplantation, while nine patients did not. These two groups were compared with respect to complications, survival, and various cytokines and factors causing vascular endothelial damage. All seven patients receiving EPA survived and only two had grade III graft-versus-host disease (GVHD). Among the nine patients not receiving EPA, three had grade III or IV GVHD. In addition, thrombotic microangiopathy developed in four patients and cytomegalovirus disease occurred in four. Five patients died in this group. The levels of leukotriene B(4), thromboxane A(2), and prostaglandin I(2) were significantly lower in patients receiving EPA than in those not receiving it (all P < 0.01). Cytokines such as tumor necrosis factor-alpha, interferon-gamma, and interleukin-10 were also significantly decreased by EPA (P < 0.05), as were factors causing vascular endothelial damage such as thrombomodulin and plasminogen activator inhibitor-1 (P < 0.05). The survival rate was significantly higher in the group given EPA (P < 0.01). EPA significantly reduced the complications of BMT, indicating that these complications may be manifestations of the systemic inflammatory response syndrome.  (+info)

17beta-estradiol increases rat cerebrovascular prostacyclin synthesis by elevating cyclooxygenase-1 and prostacyclin synthase. (79/645)

BACKGROUND AND PURPOSE: It has been reported that estrogens modulate peripheral vascular synthesis of vasodilatory hormones, including prostacyclin. If this occurs in the cerebral circulation, it could have important consequences in the modulation of cerebral hemodynamic function and improvement of stroke outcome. We investigated the hypothesis that in vivo 17beta-estradiol treatment of ovariectomized rats increases cerebrovascular prostacyclin production via elevation of the enzymes responsible for prostacyclin synthesis. METHODS: Cerebral blood vessels from 17beta-estradiol-treated and nontreated ovariectomized rats were isolated and examined for prostacyclin synthesis by enzyme-linked immunosorbent assay or for protein levels of cyclooxygenase-1, prostacyclin-synthase, and cytosolic phospholipase A2 by immunoblot analysis. RESULTS: We report that chronic in vivo 17beta-estradiol treatment significantly enhanced basal prostacyclin synthesis in rat cerebral blood vessels by 2.6-fold over control. 17beta-estradiol treatment also resulted in a 5.1-fold increase of cyclooxygenase-1 protein and a 6.7-fold increase of prostacyclin-synthase protein in the cerebral vasculature. There was no effect of estrogen on levels of cytosolic phospholipase A2. CONCLUSIONS: Our findings suggest that estrogen influences the biosynthesis of prostacyclin, which may be important in the regulation of cerebral blood flow and thrombosis. This finding may shed light on the mechanisms that govern sex-based differences in cerebrovascular disease.  (+info)

Exaggerated hypoxic pulmonary hypertension in endothelin B receptor-deficient rats. (80/645)

Mechanisms by which endothelin (ET)-1 mediates chronic pulmonary hypertension remain incompletely understood. Although activation of the ET type A (ET(A)) receptor causes vasoconstriction, stimulation of ET type B (ET(B)) receptors can elicit vasodilation or vasoconstriction. We hypothesized that the ET(B) receptor attenuates the development of hypoxic pulmonary hypertension and studied a genetic rat model of ET(B) receptor deficiency (transgenic sl/sl). After 3 wk of severe hypoxia, the transgenic sl/sl pulmonary vasculature lacked expression of mRNA for the ET(B) receptor and developed exaggerated pulmonary hypertension that was characterized by elevated pulmonary arterial pressure, diminished cardiac output, and increased total pulmonary resistance. Plasma ET-1 was fivefold higher in transgenic sl/sl rats than in transgenic controls. Although mRNA for prepro-ET-1 was not different, mRNA for ET-converting enzyme-1 was higher in transgenic sl/sl than in transgenic control lungs. Hypertensive lungs of sl/sl rats also produced less nitric oxide metabolites and 6-ketoprostaglandin F(1alpha), a metabolite of prostacyclin, than transgenic controls. These findings suggest that the ET(B) receptor plays a protective role in the pulmonary hypertensive response to chronic hypoxia.  (+info)