TXB2 Levels Research Articles

Relationship among COX-2 protein expression, PGs levels and biologic behavior in ovarian carcinoma tissues

Objective: To study the relationship among cyclooxygenase-2 (COX-2) protein expression, prostaglandins levels and biologic behavior in ovarian carcinoma tissues. Methods: The expression of COX-2 protein, levels of prostaglandin (PG)E2, 6-keto-PGF1α and thromboxane (TX)B2 in 54 biopsy specimens from patients with ovarian serous tumors which included three groups: 33 samples of ovarian serous carcinoma; 10 samples of borderline ovarian serous tumors and 11 samples of benign ovarian serous tumors and 10 samples of normal ovarian tissues were detected by Western blot analysis and radioimmunoassay to investigate their clinical significance. Results: The expression of COX-2 protein (82%, 27/33) and its relative content (20.08±3.53) in ovarian serous carcinoma tissues were statistically higher than those in benign ovarian serous tumor tissues and normal ovary tissues i.e., 0 and (15.04±0.12), 0 and (15.33±0.60) (P 0.05). The levels of PGE2, 6-keto-PGF1α and TXB2 showed no significant differences in ovarian carcinoma tissues with different clinical stages (I to II and III to IV), different histological grades, with or without ascites and lymph metastasis. COX-2 expression was correlated with the levels of PGE2, 6-KETO-PGF1α and TXB2 (P<0.01). Conclusion: Our data suggest that COX-2 overexpression leads to increased PGE2, 6-KETA-PGFPGF1α and TXB2 biosynthesis, which may be mechanisms underlying the contribution of COX-2 to the development of ovarian serous carcinoma. BGF2, 6-keto-PGF1α and TXB2 may be helpful parameters of diagnosis and differentiate diagnosis in ovarian serous carcinoma.

The PFA-100® detects sub-optimal antiplatelet responses in patients on aspirin

Although it is suspected that some patients with acute coronary syndromes (ACS) could have a sub-optimal response to aspirin (SASAR), currently a fixed dose of ASA is long-term used in all individuals. This study was designed to determine SASAR and whether a SASAR is a predictor for recurrence of ischemic events in patients on low-dose ASA with a previous ACS. One hundred patients taking ASA 100 mg/day were assessed at 1 and 6 months after a first ACS. SASAR was initially defined as a failure of the ASA treatment to significantly prolong the closure time in the Platelet Function Analyzer (PFA-100®). SASAR in these samples was reconfirmed by conventional aggregometry. TXB2 levels were determined in plasma. At one month 49 patients showed SASAR in the PFA-100®; only 25 of them showed SASAR by conventional aggregometry. At six months, 39 of 81 patients showed SASAR by PFA-100®, but conventional aggregometry detected SASAR in only 12 of the 39 patients. TXB2 levels were significantly higher in patients with SASAR. Five patients with SASAR, by both tests, died during follow-up (p=0.013). The PFA-100® detected a high rate of SASAR in patients with ACS. This instrument could be used to screen for suboptimal response to the antiplatelet action of ASA. Whether persistence of SASAR could relate to a higher risk of recurrence and how adjusting the dose of ASA could reduce the rate of SASAR are issues that deserve further investigations.

2-Arachidonoyl glycerol induces contraction of isolated rat aorta: role of cyclooxygenase-derived products.

Endocannabinoids have been shown to play a role in the regulation of vascular tone. The effects of 2-arachidonoyl glycerol (2-AG) on induced-tone were examined in rat aortic rings in vitro. Aortic rings from Wistar Kyoto (WKY) rats were suspended in organ chambers for recording isometric tension development in response to 2-AG. The production of TXA2 in response to 2-AG was also assessed by enzyme immunoassay. In endothelium-intact rings pre-contracted to PGF(2alpha), 2-AG (10 nM-30 microM) induced a biphasic effect: a weak relaxation from 10 nM to 0.1 microM, which turned into a concentration-dependent contraction from 3 to 30 microM. Endothelium-denudation did not change 2-AG-mediated vascular effects. 2-AG-induced contraction was unaffected by both the cannabinoid CB1 receptor antagonist SR141716A (3 microM) and the CB2 receptor antagonist SR144528 (1 microM). In contrast, the anandamine transport inhibitor (AM404, 100 microM) and the amino hydrolase inhibitor (PMSF, 30 microM) attenuated (P<0.05) the contractile response evoked by 2-AG in endothelium-intact and rubbed aortic rings. In addition, the cyclooxygenase inhibitor (indomethacin, 10 microM) and the thromboxane A2 (TXA2) receptor (TP receptor) antagonist GR32191 (0.3 microM) totally abolished the contraction elicited by 2-AG in endothelium-intact and rubbed aortic rings. Challenge of isolated aortic rings with 2-AG (10 microM) evoked a significant increase in TXA2 level (measured as TXB2 level) in endothelium-intact and rubbed aortic rings. These data suggested that the contraction elicited by 2-AG resulted from the vascular smooth muscle cell uptake and conversion of 2-AG to constrictor prostanoid TXA2, which in turn caused vasoconstriction through the stimulation of TP receptor.

TMVA, a novel GPIb-binding protein, significantly prevents platelet microthrombi formation and prolongs discordant cardiac xenograft survival.

In xenotransplantation, donor endothelium is the first target of immunological attack. Activation of the endothelial cell by preformed natural antibodies leads to platelet binding via the interaction of the glycoprotein (GP) Ib and von Willebrand factor (vWF). TMVA is a novel GPIb-binding protein purified from the venom of Trimeresurus mucrosquamatus. In this study, the inhibitory effect of TMVA on platelet aggregation in rats and the effect on discordant guinea pig-to-rat cardiac xenograft survival were investigated. Three doses (8, 20 or 40 microg/kg) of TMVA were infused intravenously to 30 rats respectively. Platelet aggregation rate was assayed 0.5, 12, and 24 h after TMVA administration. Wister rats underwent guinea pig cardiac cervical heterotopic transplantation using single dosing of TMVA (20 microg/kg, i.v., 0.5 h before reperfusion). Additionally, levels of TXB(2) and 6-keto-PGF(1alpha) within rejected graft tissues were determined by radioimmunoassay. Treatment with TMVA at a dose of 20 or 40 microg/kg resulted in complete inhibition of platelet aggregation 0.5 h after TMVA administration. Rats receiving guinea pig cardiac xenografts after TMVA therapy had significantly prolonged xenograft survival. Histologic and immunopathologic analysis of cardiac xenografts in TMVA treatment group showed no intragraft platelet microthrombi formation and fibrin deposition. Additionally, the ratio of 6-keto-PGF(1alpha) to TXB(2) in TMVA treatment group was significantly higher than those in control group. We conclude that the use of this novel GPIb-binding protein was very effective in preventing platelet microthrombi formation and fibrin deposition in a guinea pig-to-rat model and resulted in prolongation of xenograft survival. The increased ratio of PGI(2)/TXA(2) in TMVA treatment group may protect xenografts from the endothelial cell activation and contribute to the prolongation of xenograft survival.

Effect of a selective COX-2 inhibitor in the development of central sensitization in the oral surgery model

Nociceptive input from surgical insult and postoperative inflammation contribute to the development of central sensitization, yet their relative contributions have not been evaluated. COX-1 and -2 catalyze prostaglandin synthesis, with COX-1 being primarily responsible for PGE2 production over the first 1–2 hours with COX-2 regulation at later time points. This study evaluated the effect of COX-2 mediated prostanoid production to nociceptive input contributing to the development of central sensitization in the oral surgery model with either 50 mg rofecoxib or placebo administered preoperatively and lidocaine or long-acting bupivicaine used for local anesthesia. Microdialysis was used to collect submucosal perfusate from the surgical site for four hours postoperatively and pain report recorded concurrently. Both rofecoxib and bupivicaine suppressed pain in the immediate postoperative period independently and additively. PGE2 levels were significantly suppressed by rofecoxib as compared to placebo across the last two hours of the postoperative period (p < 0.05). TXB2 levels did not differ significantly between groups during the postoperative period. The local anesthetic did not have any effect on PGE2 or TXB2 levels. The suppression of PGE2 during the later time points suggests that inhibition of cytokine mediated postoperative inflammation limits the development of sensitization following surgery. Clinical Pharmacology & Therapeutics (2004) 75, P4–P4; doi: 10.1016/j.clpt.2003.11.014

Role of Endothelin-1 and Thromboxane A2 in the Pulmonary Hypertension Induced by Heparin–Protamine Interaction in Anesthetized Dogs

This study aimed to study the role of thromboxane A2 (TXA2) and endothelin-1 (ET-1) in the pulmonary hypertension induced by interaction of heparin-protamine in anesthetized dogs. The effect of inhaled nitric oxide (NO) was also investigated in this model. Dogs were anesthetized and instrumented for acquisition of mean arterial blood pressure, mean arterial pulmonary pressure (MPAP), and pulmonary pressure gradient (PPG). Cardiac index (CI), heart rate, and index of systemic vascular resistance were also obtained. Intravenous administration of heparin (500 IU/kg) 3 minutes before protamine (10 mg/kg) caused marked pulmonary hypertension, as evaluated by the increase in MPAP and PPG. This was accompanied by systemic hypotension, CI decrease, and tachycardia. Indomethacin (10 mg/kg), dazoxiben (10 mg/kg), or tezosentan (10-mg/kg bolus plus 10-mg/kg/h infusion) significantly reduced the increase in MPAP and PPG, but had no effect on the systemic hypotension. Similar results were obtained with inhaled NO (3 ppm). Plasma TXB2 levels were markedly elevated during the pulmonary hypertension, and this was abolished in indomethacin-treated dogs. Our study shows that interaction of heparin-protamine in anesthetized dogs lead to TXA2- and ET-1-mediated pulmonary hypertension. Drugs that interfere with the synthesis of these mediators as well as inhaled NO may be of beneficial value to control this disorder.

Urinary leukotriene E4 and 11-dehydro-thromboxane B2 excretion in children with bronchial asthma

Cysteinyl leukotrienes (CysLTs) and thromboxane (TX) A 2 have been implicated in the pathogenesis of bronchial asthma. Urinary leukotriene E 4 (LTE 4 ) and 11-dehydro-TXB 2 (11 DTXB 2 ) levels are often used to assess the production of CysLTs and TXA 2 . However, few studies have examined the products of these two mediators in the same asthmatic patients. To define the potential roles of CysLTs and TXA 2 in the pathogenesis of bronchial asthma in children, their urinary levels were measured in the present study. Urinary LTE 4 and 11DTXB 2 levels were measured by enzyme immunoassay (EIA) and radioimmunoassay (RIA), respectively. Urine samples from asthmatic children were measured during the stable condition and during an acute attack. Urinary LTE 4 levels during an acute attack (median 476 pg/mg creatinine; range 191–1100 pg/ mg creatinine) and during the stable condition (median 332 pg/mg creatinine; range 128–965 pg/ mg creatinine) were significantly higher (P < 0.05) than those of controls (median 233 pg/mg creatinine; range 103–389 pg/mg creatinine). Urinary 11DTXB 2 levels during an acute attack and during the stable condition (median 1666 (range 110–5105) and 1009 (range 46–6070) pg/mg creatinine, respectively) were significantly higher ( P < 0.05) than those of controls (median 252 pg/mg creatinine; range 41–716 pg/mg creatinine). Comparing different stages of asthma, LTE 4 levels during an acute attack were significantly higher (P < 0.05) than during the stable condition; however, there was no difference in urinary TXB2 levels. The present findings suggest that high levels of CysLTs and TXA 2 are associated with the pathogenesis of bronchial asthma. The measurement of urinary LTE 4 and 11DTXB 2 would be useful in understanding the individual pathogenesis of asthmatic children.

Effect of platelet activation and endothelial cell injury on malignant cancer

Objective: To study the effects of platelet activation and endothelial cell injury on the patients with malignant tumor and their prognoses.Methods: Radioimmunity and ELISA methods were employed to detect the TXB2, GMP-140, vWF, cGMP and FN in 78 cases of malignant tumor and 40 healthy control persons.Results: The levels of TXB2, MP-140 and cGMP were increased in intestinal cancer group, lung cancer group and hepatic cancer group, while FN decreased in intestinal cancer and lung cancer group. cGMP was positively related to TXB2, GMP-140, vWF in malignant tumor group. FN was decreased in the group complicated with infection and the group with metastasis, while the other indexes increased. GMP-140, vWF and cGMP was decreased after operation except for the increasing of FN.Conclusion: Activations of platelet and injury of endothelial cells developed in patients with malignant tumor, and both of them affected the metastasis and prognosis of malignant tumor.

Clinical implication of the changes of cAMP, TXA2 and PGI2 in CSF of asphyxiated newborns.

To evaluate the changes of 3', 5'-cyclic adenosine monophosphate (cAMP), thromboxane A2(TXA2) and prostacyclin (PGI2) in cerebrospinal fluid (CSF) in the asphyxiated newborn and explore their roles in hypoxic-ischemic brain damage (HIBD). Thirty-six full term newborns were divided into 3 groups, including 12 with moderate-severe hypoxic-ischaemic encephalopathy (HIE), 13 with mild HIE, 11 without HIE (control group). The levels of cAMP, TXB2 (TXA2 metabolite) and 6-keto-PGF1 alpha (PGI2 metabolite) in CSF and plasma were measured 36-72 h after birth by RIA, and the concentrations were expressed as nM/L (cAMP), ng/L(TXB2 and 6-keto-PGF1 alpha). The infants were followed-up at 6 and 12 month of age and Mental Development Index (MDI) and Psychomotor Development Index (PDI) were measured using Bayley Scales of Infant Development (BSID). The CSF cAMP level in moderate-severe HIE group was 8.60 +/- 2.40, significantly lower than that of the mild HIE group (14.83 +/- 2.84) and the control group (24.43 +/- 2.39) (for both P < 0.01). The levels of TXB2 and 6-keto-PGF1 alpha in CFS in the moderate-severe HIE group (206.06 +/- 29.74, 168.47 +/- 23.02, respectively) were significantly higher than in the mild HIE group (83.37 +/- 28.57, 131.42 +/- 16.57, respectively, P < 0.01) and the control group (41.77 +/- 21.58, 86.23 +/- 13.05, respectively, P < 0.01). The level changes of cAMP, TXB2 and 6-keto-PGF1 alpha in plasma in all groups were similar to those in CSF, but no significant difference was found between mild HIE group and the control group (P > 0.05). The follow-up results showed that MDI and PDI of the moderate-severe HIE group were the lowest (84.79 +/- 13.34, 83.50 +/- 13.28, respectively), followed by mild HIE group (102.19 +/- 7.02, 99.94 +/- 9.08, respectively), with the control group being the highest (116.63 +/- 12.08, 116.69 +/- 10.87, respectively). Univariate analysis showed some significant difference (the moderate-severe HIE group vs. the mild HIE group or the control group, P < 0.01; the mild HIE group vs. the control group P < 0.05). The results suggested that the concentration of cAMP, TXA2 and T/K ratio in CSF after neonatal asphyxia might be sensitive markers in evaluating the severity of brain damage in early stage and predicting the future outcome.

Mechanisms of angiotensin-converting enzyme inhibitor induced thrombolysis in Wistar rats

Our in vivo assay for thrombolysis consisted of recording the weight of platelet-rich thrombi adhering to a collagen strip that was superfused with arterial blood in extracorporal circulation of anaesthetised Wistar rats. Immediate thrombolysis occurred in response to intravenously administrated angiotensin-converting enzyme inhibitor (ACE-I) at non-hypotensive doses of 3–30 μg kg−1 (captopril<perindopril<quinapril). The thrombolytic response lasted up to 3 h with maximum reduction of the weight of thrombus by 75%. Pretreatment with COX-1 and COX-3 inhibitors (aspirin at a low dose of 1 mg kg−1, SC 560 and acetaminophen, 0.3–3 mg kg−1) slightly augmented thrombolysis by ACE-I, while COX-2 inhibitors (nimesulide and coxibs at doses <1 mg kg−1 and aspirin at a high dose of 50 mg kg−1) or a kinin B2 receptor antagonist (icatibant) abolished it. NOS inhibition by l-NAME blunted and delayed thrombolysis by ACE-I. In parallel to maximum thrombolysis by quinapril (30 μg kg−1), plasma levels of 6-keto-PGF1α rose significantly from 40±7 to 554±91 pg ml−1 (n=5, mean±S.D.), while basal levels of PGE2 (12±3 pg ml−1) and TXB2 (47±11 pg ml−1) remained essentially unchanged. Pretreatment with celecoxib (0.1–1.0 mg kg−1) abolished not only thrombolysis by quinapril but also the quinapril-induced rise in plasma 6-keto-PGF1α. In cultured bovine aortic endothelial cells, perindoprilate (30 μM) increased cytosolic free calcium [Ca2+]i, but this effect was by three to four orders of magnitude weaker than that of bradykinin (Bk). In aortas of Wistar rats, the transcripts of COX-2 and PGI-S were overexpressed as compared to COX-1. Thus, in blood vessels of Wistar rats, the preferable route of the PGI2 generation might lead through the COX-2 pathway.We conclude that in Wistar rats, ACE-I induces thrombolysis via accumulation of endogenous kinins over the endothelium and a subsequent activation of B2 receptors followed by the release of prostacyclin and nitric oxide. Thrombolysis by ACE-I seems to be mediated mainly through prostacyclin that is made by COX-2. It may well be that an increase in endothelial [Ca2+]i by ACE-I activates phospholipase A2, which supplies COX-2 with the substrate for making thrombolytic prostacyclin.

Effects of nicotine on thromboxane/prostacyclin balance in myocardial ischemia

It has been proven that nicotine contributes to cardiovascular diseases, although its precise mechanism of action is still unclear. The purpose of this study is to find how nicotine may complicate myocardial ischemia by affecting the thromboxane/prostacyclin (TXA 2/PGI 2) balance. We used four groups ( n=7 each) of isolated and perfused rabbit hearts according to Langendorff method: (i) control group; (ii) group submitted to 1 μM nicotine perfusion during 60 min; (iii) group submitted to a regional ischemia by ligation of the left descending coronary artery during 60 min and (iv) group submitted to nicotine perfusion during ischemia. Levels of TXB 2 and 6-keto PGF 1α, the stable metabolites of TXA 2 and PGI 2 were then determined in the microsomes of the hearts by radioimmunoassay. The results showed that (1) a TXA 2 synthetase activity is present in the myocardium, and this activity, as well as that of PGI 2 synthetase, is decreased by a 60 min ischemia; (2) TXA 2 and PGI 2 activities are not affected by nicotine in the normal myocardium and (3) nicotine infusion during ischemia contributes to the increase of TXA 2/PGI 2 ratio further by decreasing PGI 2. Therefore, these results provide one explanation on how nicotine might worsen myocardial ischemia.

Temporal changes in colonic vascular architecture and inflammatory mediator levels in animal models of colitis.

This study investigated the temporal relationship between inflammatory mediator production and colonic vascular architecture in rabbit and rat trinitrobenzene sulfonic acid (TNBS) models of colitis. In both species significant colonic damage and loss of mucosal integrity occurred over time. In the rabbit there was a significant increase in TxB2 levels in the muscularis propria and mucosa at 1, 6, and 48 hr after TNBS, with a significant elevation in PGE2 production in the muscularis propria at 48 hr. However, elevated mediator levels were not associated with measurable changes in vascular architecture. In contrast, significant changes in the numbers and diameters of colonic blood vessels were observed in the rat, in the absence of significant elevations in TxB2 or PGE2 levels. These data suggest that the role of lipid mediators in acute colitis is species-dependent and, although there are corresponding gross and microscopic changes in both models, these occur through disparate mechanisms.

Involvement of thromboxane A2 and peptide leukotrienes in early and late phase nasal blockage in a guinea pig model of allergic rhinitis

We investigated the effects of the thromboxane (TX) A2 antagonist seratrodast, the peptide leukotriene (p-LT) antagonist pranlukast, the antihistaminic drug terfenadine and the glucocorticoid dexamethasone on antigen-induced sneezing, biphasic nasal blockage and nasal hyperresponsiveness to histamine using a guinea pig model of allergic rhinitis. Male Hartley guinea pigs were used. Intranasally sensitized guinea pigs were challenged once every week for 13 weeks by inhalation of Japanese cedar pollen as the antigen. Dexamethasone and other agents were administered orally 3 and 1 h, respectively, before the 4th, 6th and 13th challenge. Sneezing frequency and the change in specific airway resistance (sRaw) were measured at these challenges. Two days after the 13th challenge, nasal responsiveness to histamine was evaluated by measuring sRaw after intranasal instillation of increasing doses of histamine. Moreover, the levels of TXB2, p-LTs and histamine were estimated in nasal cavity lavage fluid (NCLF) collected at the 13th challenge. Only terfenadine (10 mg/kg) significantly inhibited sneezing at any challenge time. Seratrodast (3 and 10 mg/ kg), pranlukast (30 mg/kg) and dexamethasone (10 mg/kg), but not terfenadine, suppressed both the early and late phase elevation of sRaw (biphasic nasal blockage), although the degree of inhibition on the early phase response varied with the challenge time. In contrast, the development of nasal hyperresponsiveness to histamine was inhibited by only dexamethasone. Furthermore, biphasic increases in TXB2, p-LTs and histamine in NCLF were observed after the challenge in sensitized animals. These results suggest that TXA2 and p-LTs, but not histamine, play important roles in both the early and the late phase nasal blockage in this model of allergic rhinitis.

Mechanisms in the inhibition of neointimal hyperplasia with triflavin in a rat model of balloon angioplasty

RGD-containing peptides are able to inhibit the binding of ligands to certain β3 integrins, such as αIIbβ3 and αvβ3, both of which are involved in neointimal hyperplasia. The present study was designed to elucidate the detailed mechanisms involved in the inhibition of neointimal hyperplasia with triflavin in a rat model of balloon angioplasty. Triflavin (0.25 mg·kg–1·d–1), an RGD-containing disintegrin, time dependently inhibited both neointimal hyperplasia and lumen occlusion after angioplasty in carotid arteries of rats. Furthermore, electron micrographs highlighted that SMCs were phenotypically different from the typical contractile, spindle-shaped SMCs normally seen in uninjured vessel walls. PDGF-BB was strongly produced in thrombus formation and neointimal SMCs after angioplasty, and triflavin significantly reduced PDGF-BB expression in vessel lumens and neointimal SMCs after angioplasty. Balloon angioplasty caused a significant increase of nitrate and cyclic guanosine monophosphate levels compared with levels found in sham-operated rats, and these were not significantly changed with infusion of triflavin (0.25 mg·kg–1·d–1). Furthermore, the plasma level of TXB2 obviously increased after angioplasty, and triflavin markedly suppressed the elevation of plasma TXB2 concentration. The results indicate that triflavin effectively prevents neointimal hyperplasia, possibly through the following 2 mechanisms. First, triflavin binds to αIIbβ3 integrin on platelet membranes, resulting in inhibition of platelet adhesion, secretion, and aggregation in injured arteries, followed by inhibition of TXA2 formation and PDGF-BB release from platelets. Second, triflavin may also bind to αvβ3 integrin on SMCs, thus subsequently inhibiting cell migration and proliferation. These results provide new insights into the mechanisms of neointimal hyperplasia and have significant implications for disintegrin therapy for the treatment of restenosis and atherosclerosis. (J Lab Clin Med 2001;137:270-8)

The Changes and Significance of TXA2 and PGI2 Metabolism after Rat Infrasonic Brain Damage

In this paper we study the changes and significance of the TXA2 and PGI2 metabolism after infrasonic damage to rats so as to probe the mechanism of infrasonic biological effects. Some 40 SD rats were randomized into control, infrasonic damage once, 7 times, 14 times, and treatment five groups. A stimulus of 8Hz 120dB infrasound was applied to the infrasonic damage groups for 2 hours once according to the planned times. Radioimmunoassay was used for the examination of brain TXB2 and 6-keto-PGF1a (metabolites of TSA2 and PGI2) contents. The results showed that there were no changes in TXB2 and 6-keto-PGF1a levels in the ‘once’ group while TXB2 level elevated significantly and 6-keto-PGF1a level decreased remarkably in the 7 times and the 4 times groups with an augmentation of TXA2/PGI2 value. In the treatment group both TXB2 and PGI2 levels nearly reached normal. It is concluded that the augmentation of the TXA2/PGI2 value in the 7 times and 14 times groups suggests that an imbalance in TXA2-PGI2 production contributes to the traumatic secondary processes, which include ischemia and edema. Also, the extent of TXA2 and PGI2 metabolism disturbance is closely related to the times of infrasonic injury. It is hypothesized that mGluR antagonist may exert its protective properties through increasing PGI2 production in the injured brain by improving the blood supply to injured blood vessels.

Effect of valsartan and captopril in rabbit carotid injury. Possible involvement of bradykinin in the antiproliferative action of the renin-angiotensin blockade.

The effects of the specific angiotensin II (Ang II) AT1-receptor blocker valsartan on events related to restenosis were investigated in rabbits after common carotid balloon injury. Six animals were given valsartan from two days prior to injury until 14 days post-injury. Three control groups (n=6 in each group) were either sham-operated, untreated or treated with the angiotensin-converting enzyme (ACE) inhibitor,captopril. Both ACE inhibition and AT,-receptor blockade had marked effects on plasma levels of endothelin ET1, thromboxane TXB2 and 6-keto-PGF1-alpha. The most dramatic effects on ET, levels were seen in rabbits treated with valsartan, where levels were reduced to values close to those for sham-operated animals (96.85 vs. 86.45 pg/ml). Captopril treatment led to a statistically significant (p<0.01) reduction in ET1 levels compared with untreated animals, but the reduction was only about half that seen with AT1-receptor blockade. TXB2 levels doubled (202.58 vs.413.28 pg/ml) upon arterial injury in control animals but rose by only 20-35% in rabbits treated with captopril (246.45 pg/ml) or valsartan (268.13). In untreated animals, 6-keto-PGF1-alpha levels decreased slightly after injury, but for both the captopril and valsartan groups, there were significant increases in levels of this prostaglandin derivative, effects attributed to the action of bradykinins. Levels were highest in the captopril-treated animals. Valsartan and captopril treatment led to a significant reduction in neointimal thickness and the extent of lumen stenosis compared with untreated animals. Both treatments were effective in reducing neointimal area and significantly (p<0.05)reduced cell proliferation. The differences between treatments can be attributed to the different actions of the agents, as valsartan leaves the AT2-receptor unblocked, while captopril, through inhibition of Ang II synthesis, prevents stimulation of both receptors.A combination of both treatments may be a possible way forward in the clinical prevention of restenosis.

Effects of FK3311 on Pulmonary Ischemia–Reperfusion Injury in a Canine Model

Background. This study investigated the effects of a selective COX-2 inhibitor, FK3311, on warm ischemia–reperfusion (I/R) injury in the canine lung.Materials and Methods. Sixteen adult mongrel dogs were used in this study. In the FK group (n = 8), FK (1 mg/kg) was administered intravenously 15 min before ischemia and 15 min before reperfusion. In the control group (n = 8), a vehicle was injected in the same manner. Warm ischemia was induced for 3 h by clamping the left pulmonary artery, veins, and bronchus. Five-minute clamping tests of the right pulmonary artery were performed before ischemia and 30 min after reperfusion. During the test, left pulmonary vascular resistance (L-PVR), cardiac output (CO), and arterial oxygen pressure (PaO2) were measured. The lung specimens were simultaneously harvested for wet-to-dry weight ratio (WDR) measurements, histopathological studies, and polymorphonuclear neutrophil (PMN) counts. Serum thromboxane (Tx) B2 and 6-keto-prostaglandin (PG) F1α (stable metabolites of TxA2 and PGI2, respectively) were also measured 30 min after reperfusion.Results. L-PVR, CO, PaO2, and WDR were significantly (P < 0.05) better in the FK group than in the control group. Histological tissue edema was mild, and PMN infiltration was significantly (P < 0.05) reduced in the FK group compared to the control group. The serum TxB2 levels were significantly (P < 0.05) lower in the FK group than in the control group, while 6-keto-PGF1α levels were not significantly (P < 0.05) reduced. Two-day survival rate was significantly (P < 0.05) better in the FK group than in the control group.Conclusions. FK has protective effects on pulmonary I/R injury stemming from marked inhibition of TxA2.

Hepatic oxygen exchange and energy metabolism in hyperdynamic porcine endotoxemia: effects of the combined thromboxane receptor antagonist and synthase inhibitor DTTX30.

We compared the effects of thromboxane receptor antagonist and synthase inhibitor DTTX30 on systemic and liver blood flow, oxygen (O2) exchange and energy metabolism during 24 h of hyperdynamic endotoxemia with untreated endotoxemia. Prospective, randomized, experimental study with repeated measures. Investigational animal laboratory. Twenty-seven domestic pigs: 16 during endotoxemia with volume resuscitation alone; 11 with endotoxemia, volume resuscitation and treatment with DTTX30. Continuous infusion of Escherichia coli lipopolysaccharide (LPS) for 24 h together with volume resuscitation. After 12 h of endotoxemia, DTTX30 was administered as a bolus of 0.12 mg kg-1 followed by 12 h continuous infusion of 0.29 mg kg-1 per h. DTTX30 effectively counteracted the endotoxin-associated increase in TXB2 levels and increased 6-keto-PGF1 alpha with a significant shift of the thromboxane/prostacyclin ratio towards predominance of prostacyclin. DTTX30 prevented the significant progressive endotoxin-induced decrease of mean arterial pressure (MAP) below baseline while maintaining cardiac output (CO), and increased the fractional contribution of liver blood flow to CO without an effect on either hepatic O2 delivery or O2 uptake. The mean capillary hemoglobin O2 saturation (HbO2) on the liver surface and HbO2 frequency distributions remained unchanged as well. DTTX30 significantly attenuated the endotoxin-induced derangements of cellular energy metabolism as reflected by the diminished progressive decrease in hepatic lactate uptake rate and a blunted increase in hepatic venous lactate/pyruvate ratios. While endotoxin significantly increased the endogenous glucose production (EGP) rate, EGP returned towards baseline levels in the DTTX30-treated group. Thus, in our model DTTX30 resulted in hemodynamic stabilization concomitant with improved hepatic metabolic performance.

Sulfidopeptide leukotrienes, but not thromboxane B2 or histamine, are elevated in sputum during exacerbation of asthma

Although sulfidopeptide leukotrienes (sLT) are considered to play an important role in the pathogenesis of asthma, their precise action has not been elucidated in asthmatics during exacerbation. In the present study, we examined sputum concentrations of sLT from asthmatic patients in order to determine whether sLT are actively involved in the exacerbation of asthma. We also examined sputum levels of thromboxane (TX) B2 and histamine because these mediators are considered to be as important as sLT. The induced sputa by 3% hypertonic saline inhalation were treated with high-performance liquid chromatography and levels of sLT, TXB2 and histamine were measured with enzyme immunoassay kits. These compounds tended to be elevated in asymptomatic asthmatic patients compared with healthy controls, but the differences were not significant. Levels of sLT and TXB2 showed no difference between atopic and non-atopic patients, but histamine levels were higher in atopic patients than in non-atopic patients. However, sputa during the exacerbation contained significantly higher levels of sLT than those during the asymptomatic state. In contrast, neither histamine nor TXB2 showed any changes with exacerbation. These results suggest that sLT may be one of the most potent for mounting the exacerbation of asthma.

Effects of olopatadine hydrochloride on the release of thromboxane B2 and histamine from nasal mucosa after antigen–antibody reaction in guinea pigs

Various mediators, such as thromboxane (TX) A 2 , peptide leukotrienes (P-LT) and histamine, are involved in allergic nasal obstruction. The aim of the present study was to investigate the mechanism whereby olopatadine hydrochloride, a novel anti-allergic drug, ameliorated the allergic nasal obstruction. The levels of TXB 2 , P-LT and histamine in nasal lavage fluid (NLF) were measured after intranasal antigen challenge in sensitized guinea pigs. Histamine and TXB 2 levels in the NLF increased eight- and threefold, respectively, 10 min after antigen challenge, whereas the P-LT level was under the detection limit. Oral administration of olopatadine at 0.1, 1 and 3 mg/kg significantly inhibited the increases in TXB 2 and histamine levels. At 3 mg/kg, olopatadine also ameliorated the nasal obstruction caused 10 min after antigen challenge, as determined by acoustic rhinometry. These results suggest that the amelioration by olopatadine of the allergic nasal obstruction involves the inhibition of the release of TXA 2 and histamine.