Excretion Of Thromboxane B2 Research Articles

Obesity-like metabolic effects of high-carbohydrate or high-fat diets consumption in metabolic and renal functions

Present study investigated which diet, high-carbohydrate (HCD) or high-fat (HFD), most effectively induces classical characteristics of obesity in mice. Mice were fed commercial chow (control), an HCD, or an HFD for 12 weeks. HFD and HCD increased body weight, fat mass, and glycaemia, whereas the HFD augmented insulinemia. In the kidney, the HFD caused albuminuria, and reductions in fractional Na+ excretion, Thromboxane B2 (TXB2) excretion, and urinary flow, whereas the HCD reduced glomerular filtration, plasma osmolality, and TXB2 and Prostaglandin E2 excretion. The consumption of HFD and HCD modified parameters that indicate histopathological changes, such as proliferation (proliferating-cell-nuclear antigen), inflammation (c-Jun N-terminal-protein), and epithelial-mesenchymal transition (vimentin, and desmin) in renal tissue, but the HCD group presents fewer signals of glomerular hypertrophy or tubule degeneration. In summary, the HCD generated the metabolic and renal changes required for an obesity model, but with a delay in the development of these modifications concerning the HFD.

Enhanced urinary excretion of thromboxane B2 in non-alcoholic fatty liver disease. Implication for antiplatelet treatment

Aim: Non-alcoholic fatty liver disease (NAFLD) represents the most common liver disease worldwide. Patients with NAFLD are at high risk for cardiovascular diseases that represents the major cause of morbidity and mortality in this setting. Platelets play a key role in precipitating atherosclerotic complications as indicated by interventional studies with aspirin, which significantly reduces cardiovascular events by impairing platelet Thromboxane B2 (TxB2) biosynthesis. We investigated the behaviour of platelet activation in patients with NAFLD.

Influence of the selective COX-2 inhibitor celecoxib on sex differences in blood pressure and albuminuria in spontaneously hypertensive rats

We previously reported that female spontaneously hypertensive rats (SHR) have greater cyclooxygenase-2 (COX-2) expression in the renal medulla and enhanced urinary excretion of prostaglandin (PG) E2 (PGE2) metabolites compared to male SHR. Based on the role of COX-2-derived prostanoids in the regulation of cardiovascular health, the aim of the current study was to test the hypothesis that blood pressure (BP) in female SHR is more sensitive to COX-2 inhibition than in males. Seven week old male and female SHR were implanted with telemetry transmitters for continuous BP recording. After one week of baseline BP recording, male and female SHR were randomized to receive the selective COX-2 inhibitor celecoxib (10 mg/kg/day) or vehicle for six weeks (from 9 to 14 weeks of age). Female SHR had lower BP and albuminuria compared to male SHR as well as enhanced urinary excretion of PGE metabolite (PGEM), 6-keto PGF1α and thromboxane B2, indicators of PGE2, PGI2 and TXA2, respectively. Treatment with celecoxib did not significantly alter BP or albuminuria in either female or male SHR. Celecoxib did not change PGs metabolites excretion in male SHR; however, excretion levels of PGEM and 6-keto PGF1α were reduced in female SHR. COX-2 derived PG can also induce oxidative stress. Markers of oxidative stress (thiobarbituric acid reactive substances (TBARs) and H2O2 excretion) were lesser in female SHR versus male SHR. Celecoxib treatment did not significantly change markers of oxidative stress in female SHR, however, urinary TBARs excretion was significantly reduced in male SHR after 6 weeks of treatment with celecoxib. Therefore, although celecoxib treatment appears to have distinct effects on prostanoids levels in female SHR vs. males, it is unlikely that COX-2 contributes to established sex differences in BP in SHR.

Effect of rapid desensitization on platelet inhibition and basophil activation in patients with aspirin hypersensitivity and coronary disease

To determine antiplatelet efficacy after desensitization in patients with a history of aspirin hypersensitivity. We conducted a case-control study to evaluate the efficacy of aspirin 1 day (D1) and 6-8 weeks (W6-8) after desensitization. We also assessed ex vivo basophil reactivity to aspirin after desensitization. Cases were patients with coronary artery disease (CAD) and documented history of aspirin hypersensitivity who underwent rapid successful oral desensitization to aspirin. Controls were patients with stable CAD without hypersensitivity and receiving aspirin. Among 56 cases, 27 received aspirin for acute coronary syndromes and 29 were treated for stable CAD. Aspirin was effective (defined as light transmission aggregometry induced by arachidonic acid ≤20%) at D1 in 86% of cases (P = 0.045 vs. controls) and in 95% at W6-8, vs. 100% of controls (P = 0.39). Urinary excretion of thromboxane B2 diminished substantially in cases (P < 0.0001, D0 vs. W6-8) but remained higher than in controls (P = 0.03). Platelet reactivity (defined by platelet P-selectin expression, activated glycoprotein IIb/IIIa inhibitors, and platelet-monocyte aggregates) was similar in cases between D0 and D1 but decreased at W6-8. Basophil activation (quantified by upregulation of CD203c in response to aspirin) was higher in cases at W6-8 than in controls (P = 0.0002). Thus, following rapid desensitization, aspirin achieves rapid biological efficacy, which is slightly lower at D1, but becomes indistinguishable from chronically treated patients at W6-8. Persistent basophil activation several weeks after desensitization suggests infraclinical hypersensitivity and the need to continue aspirin to maintain desensitization.

Renal protective effect of chronic inhibition of COX-2 with SC-58236 in streptozotocin-diabetic rats

The induction of renal cyclooxygenase-2 (COX-2) in diabetes has been implicated in the renal functional and structural changes in models where hypertension or uninephrectomy was superimposed. We examined the protective effects of 3 mo treatment of streptozotocin-diabetic rats with a highly selective COX-2 inhibitor (SC-58236) in terms of albuminuria, renal hypertrophy, and the excretion of TNF-α and TGF-β, which have also been implicated in the detrimental renal effects of diabetes. SC-58236 treatment (3 mg·kg(-1)·day(-1)) of diabetic rats resulted in reduced urinary excretion of PGE(2), 6-ketoPGF(1α), and thromboxane B(2), all of which were increased in the diabetic rat compared with age-matched nondiabetic rats. However, serum thromboxane B(2) levels were unchanged, confirming the selectivity of SC-58236 for COX-2. The renal protective effects of treatment of diabetic rats with the COX-2 inhibitor were reflected by a marked reduction in albuminuria, a reduction in kidney weight-to-body weight ratio, and TGF-β excretion and a marked decrease in the urinary excretion of TNF-α. The protective effects of SC-58236 were independent of changes in plasma glucose levels or serum advanced glycation end-product levels, which were not different from those of untreated diabetic rats. In an additional study, the inhibition of COX-2 with SC-58236 for 4 wk in diabetic rats resulted in creatinine clearance rates not different from those of control rats. These results confirm that the inhibition of COX-2 in the streptozotocin-diabetic rat confers renal protection and suggest that the induction of COX-2 precedes the increases in cytokines, TNF-α, and TGF-β.

Leukocyte count is associated with increased platelet reactivity and diminished response to aspirin in healthy individuals with a family history of coronary artery disease

Background Markers of systemic inflammation, including blood leukocyte count, are associated with increased cardiovascular risk, but the mechanisms underlying this association are unclear. Leukocytes may promote platelet reactivity and thrombus formation, providing a basis for increased risk, but a relation between leukocyte count and platelet function has not been studied. Methods We evaluated the relation of blood leukocyte count, C-reactive protein (CRP), and interleukin-6 (IL-6) to platelet aggregation to collagen, ADP and arachidonic acid, and to urinary excretion of 11-dehydro thromboxane B2. Studies were conducted in 1600 individuals (45.0 ± 12.9 years, 42.7% male) at risk for coronary artery disease (CAD) before and after low dose aspirin. Results At baseline, platelet reactivity increased with increasing quartile of leukocyte count (median counts for each quartile were normal) for all measures of platelet function ( P < 0.0001). These relations were unchanged by aspirin. The relation between leukocyte count and each measure of platelet reactivity remained significant ( P < 0.05) after multivariable adjustment for CRP, IL-6, cardiac risk factors, hematologic variables, and platelet thromboxane production. CRP and IL-6 were independently associated with few measures of platelet reactivity. Conclusions Increasing quartile of leukocyte count, even within the normal range, is associated with increasing platelet reactivity in individuals at risk for CAD. This relationship is not altered by aspirin and is independent of inflammatory markers and platelet thromboxane production. Additional studies are needed to determine the mechanism(s) for this association and therapies to reduce cardiovascular risk in patients with elevated leukocyte counts.

Aspirin therapy and thromboxane biosynthesis in systemic lupus erythematosus

Incomplete suppression of thromboxane biosynthesis during aspirin therapy is associated with increased cardiovascular risk. Since systemic lupus erythematosus (SLE) is associated with platelet activation and increased cardiovascular mortality, we compared thromboxane and prostacyclin biosynthesis in patients with SLE and control subjects, and measured inhibition of thromboxane excretion in aspirin-treated subjects. We measured the urinary excretion of 11-dehydro thromboxane B( 2) (TXB(2)) and 2,3-dinor 6-ketoPGF(1alpha) (PGI-M), the stable metabolites of thromboxane A(2) and prostacyclin, respectively, in 74 patients with SLE and 70 controls. In subjects who were not receiving aspirin, TXB(2) excretion was higher in patients with SLE [0.40 ng/mg creatinine (0.26-0.64), median (interquartile range)] than controls [0.31 ng/mg creatinine (0.23-0.44)] (P = 0.04), and in these patients, TXB(2) excretion correlated with disease activity (rho = 0.28, P = 0.03) and tumor necrosis factor alpha (rho = 0.48, P < 0.001). Aspirin therapy resulted in significantly lower TXB(2) excretion in controls (P = 0.01), but not in patients with SLE (P = 0.10), compared with subjects not receiving aspirin. Prostacyclin biosynthesis did not differ among patients and controls, and was not affected by aspirin (P all >0.35). Thromboxane biosynthesis is increased in SLE and is associated with disease activity. Additionally, response to aspirin may be attenuated in some patients with SLE.

The Paradox of Platelet Activation and Impaired Function: Platelet-von Willebrand Factor Interactions, and the Etiology of Thrombotic and Hemorrhagic Manifestations in Essential Thrombocythemia and Polycythemia Vera

Patients with essential thrombocythemia (ET) and polycythemia vera (PV), complicated by microvascular ischemic or thrombotic events, have shortened platelet survival, increased beta-thromboglobulin, platelet factor 4, and thrombomodulin levels, and increased urinary thromboxane B2 excretion. These are all reversible by inhibition of platelet cyclooxygenase 1 with aspirin, and are therefore indicative of platelet activation and platelet-mediated thrombotic processes. The thrombotic tendency persists as long as platelet counts are above the upper limit of normal (400 x 10 (9)/L). Despite strong evidence of in vivo platelet activation, the ex vivo platelet function tests are impaired. Platelet dysfunction in ET and PV typically is characterized by a missing second-wave adrenaline aggregation, an increased adenosine diphosphate aggregation threshold, and reduced secretion products, but a normal arachidonic acid or collagen-induced aggregation. The proposed concept is that platelets in thrombocythemia (ET and PV) are hypersensitive. Due to the existing high shear stress in the microvasculature (end-arterial circulation), platelets spontaneously activate, secrete their products, form aggregates mediated by von Willebrand factor (vWF) that transiently plug the microcirculation, deaggregate, and then recirculate as exhausted defective platelets with secondary storage pool disease on ex vivo analysis. At increasing platelet counts from below to above 1000 x 10 (9)/L, the thrombotic condition changes into an overt spontaneous bleeding tendency as a result of a functional vWF deficiency that is caused by proteolysis of large vWF multimers. This is consistent with acquired type 2 von Willebrand syndrome (AvWS). AvWS is reversible by reduction of the platelet count to normal. The acquired JAK2 V617F gain of function mutation is the cause of trilinear myeloproliferative disease with the sequential occurrence of ET and PV. Heterozygous JAK2 V617F mutation with slightly increased kinase activity is enough for the induction of spontaneous megakaryopoiesis and erythropoiesis, and an increase of hypersensitive platelets is the cause of aspirin-sensitive, platelet-mediated microvascular ischemic and thrombotic complications in ET and early PV mimicking ET. Homozygous JAK2 mutation with pronounced increase of kinase activity is associated with pronounced trilinear megakaryocyte, erythroid, and granulocytic myeloproliferation, with the most frequent clinical picture of classical PV complicated by major thrombosis, in addition to the platelet-mediated microvascular thrombotic syndrome of thrombocythemia.

Clinical and Laboratory Features, Pathobiology of Platelet-Mediated Thrombosis and Bleeding Complications, and the Molecular Etiology of Essential Thrombocythemia and Polycythemia Vera: Therapeutic Implications

Microvascular disturbances in essential thrombocythemia (ET) and polycythemia vera (PV), including erythromelalgia, and atypical and typical transient cerebral, ocular, and coronary ischemic attacks, are caused by platelet-mediated transient and occlusive thrombosis in the end-arterial circulation. ET patients with microvascular disturbances have shortened platelet survival, increased beta-thromboglobulin (beta-TG), platelet factor 4 (PF4), and thrombomodulin (TM) levels, and increased urinary thromboxane B2 (TXB2) excretion, indicating platelet-mediated thrombotic processes. Inhibition of platelet cyclooxygenase-1 by aspirin is followed by relief of microvascular disturbances; correction of shortened platelet survival; correction of increased plasma beta-TG, PF4, and TM levels; and correction of increased TXB2 excretion to normal. In PV associated with thrombocythemia, increased hematocrit and whole blood viscosity aggravate the platelet-mediated microvascular syndrome of thrombocythemia to produce major arterial and venous thrombotic complications. Correction of hematocrit to normal by phlebotomy will reduce the major arterial and venous thrombotic complications, but fails to prevent the platelet-mediated microvascular circulation disturbances in PV patients because thrombocythemia persists. Complete relief and prevention of microvascular and major thrombosis in ET and PV patients, in addition to phlebotomy, are obtained by treatment with aspirin and not with coumarin. The discovery of JAK2 V617F gain of function mutation in patients with myeloproliferative disorders (MPDs) expands our insights into the molecular etiology and biological features of ET, PV, and chronic idiopathic myelofibrosis (CIMF). The current concept is that heterozygous JAK2 V617F mutation with increased kinase activity is enough for megakaryocyte proliferation and increased hypersensitive platelets with no or slightly increased erythropoiesis in ET and in early PV mimicking ET. Homozygous JAK2 mutation with pronounced kinase activity is associated with trilinear megakaryocyte, erythroid, and granulocytic myeloproliferation, myeloid metaplasia, and secondary myelofibrosis (MF), with the most frequent clinical picture of classical PV complicated by major thrombosis in addition to the platelet-mediated microvascular thrombotic syndrome of thrombocythemia. The positive predictive value of a JAK2 V617F polymerase chain reaction test for the diagnosis of MPDs is high (near to 100%), but only half of ET and MF (sensitivity 50%) and the majority of PV (sensitivity 85 to 97%) are JAK2 V617F positive. Bone marrow histopathology, when used in combination with specific markers such as serum erythropoietin, PRV-1, endogenous erythroid colony formation, peripheral blood parameters and red cell mass, has a high sensitivity and specificity (near 100%) to detect the early and overt stages of the MPDs and to differentiate between ET, PV, and CIMF in both JAK2 V617F-positive and -negative MPDs.

Cyclooxygenase‐2 inhibition ameliorates early renal injury in Han:SPRD‐ cy rats with inherited kidney disease

Selective cyclooxygenase-2 (COX-2) inhibition appears to be renoprotective in some models of kidney disease, but not in others. The objective of our study was to examine the effects of COX-2 inhibition in a rat model of chronic kidney disease. Four week old Han:SPRD-cy rats were given either a standard rodent diet containing 3mg/kg body weight NS-398 (a selective COX-2 inhibitor) or a control diet with no drug for 7 weeks. Morphometric and immunohistochemical analyses revealed that NS-398 fed animals had reduced renal fibrosis, macrophage infiltration, epithelial cell proliferation and oxidant injury, compared to control fed animals. COX-2 inhibition did not alter the degree of cystic change or creatinine clearance. Kidney disease was associated with higher renal COX-1 and -2 enzyme activities. Treatment with NS398 blunted this increase in enzyme activity only for COX-2 (as indicated by 26% lowerrenal prostaglandin E2 (PGE2), 29% lower 6-keto-prostaglandin F1α (6-keto-PGF1α) and 28% lower total prostanoid production). NS398 decreased urinary excretion of thromboxane B2, PGE2 and 6-keto-PGF1α. In conclusion, COX-2 inhibition reduces the elevated renal COX-2 activity, prostanoid production and attenuates renal injury in this rat model of chronic renal disease. (Supported by funding from the Natural Sciences and Engineering Research Council of Canada)

Platelet-mediated erythromelalgic, cerebral, ocular and coronary microvascular ischemic and thrombotic manifestations in patients with essential thrombocythemia and polycythemia vera: A distinct aspirin-responsive and coumadin-resistant arterial thrombophilia

Microvascular circulation disturbances including erythromelalgia, its microvascular ischemic complications, and migraine-like atypical or typical transient ischemic cerebral, ocular, and coronary ischemic attacks are specific clinical manifestations in patients with essential thrombocythemia (ET), and polycythemia vera (PV) associated with thrombocythemia. Thrombocythemia (ET and PV) patients with microvascular disturbances have shortened platelet survival, increased β-thromboglobulin (β-tg), platelet factor 4 (PF4), and thrombomoduline (TM) levels, and increased urinary thromboxane B2 (TxB2) excretion indicating platelet-mediated processes in vivo. Inhibition of platelet cyclooxygenase (COX 1) by aspirin is followed by relief of microvascular disturbances, correction of shortened platelet survival, and return of plasma levels of β-tg, PF4, TM levels and TxB2 excretion to normal. The transient ischemic attacks and thrombotic complications in thrombocythemia are very likely caused by hypersensitive platelets produced by spontaneously proliferating enlarged megakaryocytes in the bone marrow of ET and PV patients. In contrast to normal platelets in healthy individuals the circulating hypersensitive thrombocythemic platelets spontaneously activate and secrete their products, thus forming aggregates that transiently plug the microcirculation, or result in occlusive platelet thrombi in arterioles or small arteries. Clear evidence is presented that the microvascular transient ischemic and occlusive thrombotic complications in thrombocythemia patients are relieved by treatment with aspirin and by reduction of platelet counts to normal (<400 × 109/l), but not by coumadin. In patients with thrombocythemia associated with PV, increased hematocrit and whole blood viscosity aggravate the platelet-mediated microvascular ischemic and thrombotic syndrome of thrombocythemia to major arterial and venous thrombotic complications. Correction of hematocrit and blood viscosity by phlebotomy significantly reduces the major arterial and venous thrombotic complications, but fails to prevent the platelet-mediated microvascular circulation disturbances in PV patients because thrombocythemia persists. Complete relief and prevention of microvascular and major thrombosis in PV patients are obtained by treatment with low-dose aspirin on top of phlebotomy or by treatment with the platelet lowering agents, anagrelide, interferon or hydroxyurea.

Issue Highlights

HomeCirculationVol. 112, No. 7Issue Highlights Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIssue Highlights Originally published16 Aug 2005https://doi.org/10.1161/circ.112.7.935Circulation. 2005;112:935REAL-TIME THREE-DIMENSIONAL ECHOCARDIOGRAPHY: A NOVEL TECHNIQUE TO QUANTIFY GLOBAL LEFT VENTRICULAR MECHANICAL DYSSYNCHRONY, by Kapetanakis et al.Left ventricular (LV) dyssynchrony is recognized as being an important contributor to LV dysfunction in patients with wide QRS complexes. Optimal evaluation of patients with dyssynchrony is uncertain, and various techniques have been described to identify appropriate candidates for cardiac resynchronization therapy (CRT) and to optimize settings after implantation. Kapetanakis et al describe a real-time 3-dimensional echocardiography technique in which global and regional volume and function are assessed in 89 healthy volunteers and 174 patients with and without LV dysfunction. A dyssynchrony index of the entire LV is derived that increases with worsening LV function irrespective of QRS duration. In 26 patients treated with CRT, the dyssynchrony index improves, and this correlates with reverse remodeling. This real-time, 3-dimensional, echo technique may help to quantify objectively the degree of dyssynchrony, direct CRT settings, and identify a larger group of patients with dyssynchrony in the absence of increased QRS duration. See p 992.CONTRIBUTION OF CYCLOOXYGENASE-2 TO ELEVATED BIOSYNTHESIS OF THROMBOXANE A2 AND PROSTACYCLIN IN CIGARETTE SMOKERS, by McAdam et al.In recent months, we have experienced an intense and fierce debate about the cardiovascular safety of COX-2 inhibitors. One of the issues in this context is their effects on the biosynthesis of prostaglandins. In this issue of Circulation, McAdam et al report on the effects of rofecoxib at a high dose on the biosynthesis of thromboxane A2 and prostacyclin in smokers and nonsmokers. Prostacyclin metabolites were increased in smokers and were reduced by rofecoxib; this also occurred to some degree in nonsmokers. Furthermore, the metabolites of thromboxane were increased in smokers and reduced by rofecoxib in smokers but not in nonsmokers. In contrast to the urinary excretion of thromboxane B2, plasma levels of thromboxane did not differ in smokers and nonsmokers and were unaffected by rofecoxib. This study demonstrates that, particularly in smokers, the increase in the biosynthesis of prostacyclin is largely derived from cyclooxygenase-2. Inhibition of this most likely compensatory mechanism in this group of patients at high risk for cardiovascular effects by COX-2 inhibitors may be disadvantageous in this context and potentially may facilitate thrombus formation in smokers. See p 1024.BILIRUBIN: A NATURAL INHIBITOR OF VASCULAR SMOOTH MUSCLE CELL PROLIFERATION, by Öllinger et al.Atherosclerosis is a disorder associated with vascular stress response, and heme oxygenase induction is one component of vascular stress. Considerable data demonstrate that induction of heme oxygenase ameliorates many features of vascular disease. The mechanism(s) responsible for such observations, however, have been unclear. In this issue, Öllinger and colleagues have examined the biological activity of a heme oxygenase product, bilirubin, with regard to vascular injury and smooth muscle cell proliferation. This study increases our understanding of how heme oxygenase induction may limit the vascular injury response. See p 1030.Visit http://www.circ.ahajournals.org:Clinician UpdateShould Aspirin Be Discontinued Before Coronary Artery Bypass Surgery? See p e85.Images in Cardiovascular MedicinePrinzmetal Angina in an Adolescent: Adjunctive Role of Tissue Synchronization Imaging. See p e91.Visualization of Regional Left Ventricular Mechanical Delay by Tissue Synchronization Imaging in Heart Failure Patients With Wide and Narrow QRS Complexes Undergoing Cardiac Resynchronization Therapy. See p e93.Adult Patient With Isolated Noncompaction of Ventricular Myocardium. See p e96. Download figureDownload PowerPointBook ReviewInside the FDA: The Business and Politics Behind the Drugs We Take and the Food We Eat. See p e98.CorrespondenceSee p e99. Previous Back to top Next FiguresReferencesRelatedDetails August 16, 2005Vol 112, Issue 7 Advertisement Article InformationMetrics https://doi.org/10.1161/circ.112.7.935 Originally publishedAugust 16, 2005 PDF download Advertisement

Sexual Dimorphism in Renal Production of Prostanoids in Spontaneously Hypertensive Rats

Male spontaneously hypertensive rats (SHR) have higher blood pressure, blunted pressure-natriuresis relationship, and accelerated progression of renal injury compared with female SHR. Renal medullary prostanoids mediate vascular tone, salt and water balance, and renin release and, as a result, are involved in the maintenance of renal blood flow and the pathogenesis of hypertension. The aim of this study was to determine whether a gender difference exists in prostanoid production in SHR and whether sex steroids influence prostaglandin (PG) production. Thirteen-week-old intact and gonadectomized male and female SHR rats were placed in metabolic cages for 24-hour urine collection. Prostanoid excretion was determined using enzyme immunoassay. Kidneys were isolated and separated into outer and inner medulla for Western blot analysis. Female SHR had enhanced urinary excretion of PG E2 (PGE2) metabolites and thromboxane B2, an indicator of renal thromboxane production, compared with male SHR. There were no gender differences in excretion of systemic thromboxane or prostacyclin. Correspondingly, female SHR had enhanced microsomal PGE2 synthase protein expression in the renal inner medulla and greater cyclooxygenase-2 (COX-2) expression in the outer medulla. Orchidectomy was associated with increased PGE2 metabolite excretion and microsomal PGE synthase protein expression. Thromboxane B2 excretion was not affected by gonadectomy in either male or female SHR. Protein expressions of COX and cytoplasmic PGE2 synthase in the renal medulla were unchanged by gonadectomy in both sexes. These results demonstrate a sexual dimorphism in renal production of prostanoids in SHR and that PGE production is testosterone sensitive and estrogen insensitive.

Rofecoxib decreases renal injury in obese Zucker rats.

The present study tested the hypothesis that altered vascular regulation of arachidonic acid enzymes in obese Zucker rats contributes to renal damage. Protein expression of CYP450 (cytochrome P450) and COX (cyclo-oxygenase) enzymes in renal microvessels was studied in obese and lean Zucker rats at 20-21 weeks of age. Body weight and blood glucose averaged 649+/-13 g and 142+/-10 mg/dl in obese Zucker rats compared with 437+/-10 g and 111+/-5 mg/dl in age-matched lean Zucker rats. Renal microvascular CYP4A and COX-2 protein levels were increased and CYP2C protein levels decreased in obese Zucker rats. TX (thromboxane) B2 excretion was 2-fold higher and PG (prostaglandin) E2 excretion significantly lower in obese Zucker rats. Additional studies investigated the ability of the COX-2 inhibitor, rofecoxib, to slow the progression of renal injury in obese Zucker rats. Rofecoxib treatment decreased urinary PGF2alpha and 8-isoprostane levels in obese Zucker rats. Renal microvessel mRNA expression of pro-inflammatory chemokines was decreased in COX-2-inhibitor-treated obese Zucker rats. Urinary albumin excretion, an index of kidney damage, averaged 95+/-11 mg/day in vehicle-treated and 9+/-1 mg/day in rofecoxib-treated obese Zucker rats. Glomerulosclerosis, characterized by mesangial expansion, tubulo-interstitial fibrosis and extracellular matrix accumulation, was prominent in obese Zucker rats compared with a lack of damage in age-matched lean Zucker rats and rofecoxib-treated obese Zucker rats. These results suggest that altered vascular arachidonic acid enzymes contribute to the renal damage, and that COX-2 inhibition decreases glomerular injury in obese Zucker rats.

L-arginine reverses p47phox and gp91phox expression induced by high salt in Dahl rats.

Derangements in the production and degradation of reactive oxygen species (ROS) as well as nitric oxide (NO) have been implicated in cardiovascular diseases. We explored how supplementation with l-arginine, an NO synthase substrate, restores such derangements of ROS/NO systems in Dahl salt-sensitive, hypertensive (DS) rats. We detected an increase of NADPH oxidase activity, a key enzyme that produces superoxide, in the membrane fraction of the renal cortex derived from DS rats loaded with high salt for 4 weeks; high salt loading also remarkably increased urinary H2O2, 8-isoprostane, and thromboxane B2 excretion and decreased plasma NO end products. These changes from high salt loading were counteracted by oral l-arginine supplementation. We further examined expression patterns of NADPH oxidase subunits in renal cortex derived from these animals. High salt loading increased gp91phox and p47phox but not p22phox or Rac1 or mRNA abundance, which were counteracted with L-arginine supplementation. Western blot analyses after subcellular fractionation revealed that l-arginine supplementation distinctly decreases membrane localization of p47phox protein, as it decreases total expression of Rac1 protein in DS rats with high salt loading. These results disclose that high salt loading causes a deficiency in available L-arginine amounts for NO synthases and induces NADPH oxidase activation in the renal cortex of DS rats, which l-arginine supplementation markedly restores. Since superoxide rapidly eliminates NO, which inhibits sodium reabsorption in the cortical collecting duct, superoxide production caused by upregulated NADPH oxidase activity in the renal cortex of high salt-loaded DS rats may accelerate sodium reabsorption and hypertension.

Platelet-mediated microvascular inflammation and thrombosis in thrombocythemia vera: a distinct aspirin-responsive arterial thrombophilia, which transforms into a bleeding diathesis at increasing platelet counts

Erythromelalgia is the main, pathognomonic and presenting symptom in patients with essential thrombocythemia and thrombocythemia associated with polycythemia vera. Complete relief from erythromelalgic and acrocyanotic pain is obtained with the cyclooxygenase inhibitors aspirin and indomethacin, but not with sodiumsalicylate, dipyridamol, sulfinpyrozone and ticlopedine. Thus, cyclooxygenase metabolites are necessary for erythromelalgia to develop. Local platelet consumption in erythromelalgic areas became evident by the demonstration of arteriolar fibromuscular intimal proliferation and occlusions by platelet-rich thrombi in skin biopsies, by the findings of shortened platelet survival times, significant higher levels of platelet activation markers β-thromboglobulin, thrombomoduline and increased urinary thromboxane B2 excretion in thrombocythemia patients suffering from erythromelalgia. Aspirin treatment of erythromelalgia in thrombocythemia patients resulted in the disappearance of the erythromelalgic, thrombotic signs and symptoms, correction of the shortened platelet survival times, and a significant reduction of the increased levels of β-TG, PF4, TM and urinary TxB2 excretion to normal. Erythromelalgia is frequently preceded or followed by atypical transient neurologic, ocular or coronary ischemic symptoms, which specifically respond to low-dose aspirin or reduction of platelet counts to normal. The broad spectrum of acropareshesias, erythromelalgia and acrocyanotic ischemia together with the episodic and transient atypical TIAs and ocular or coronary ischemic symptoms are caused by spontaneous activation and aggregation of hypersensitive platelets in the end-arterial microvasculature involving the peripheral, cerebral and coronary circulation of thrombocythemia patients. These microvacular circulation ischemic disturbances in thrombocythemia vera already occur at platelet counts in excess of 400 × 10 9 l –1. Low-dose aspirin is highly effective and safe in the cure and prevention of thrombotic and ischemic events and does not elicit bleedings at platelet counts below 1000 × 10 9 l –1. Spontaneous hemorrhages usually occur at very high platelet counts far in excess of 1000 × 10 9 l –1 (HT) due to an acquired von Willebrand factor deficiency at increasing platelet counts. At platelet counts between 1000 and 2000 × 10 9 l –1, thrombosis and bleeding (ETT and HT) frequently occur in sequence or paradoxically and low-dose aspirin does prevent thrombotic complications but aggravates or may elicit bleeding symptoms. Reduction of the platelet count to below 1000 × 10 9 l –1 by platelet lowering agents usually results in the disappearance of the bleeding tendency and improvement of the von Willebrand syndrome, but the thrombotic tendency persists as long as platelet counts are above the upper limit of normal.

Dietary chloride does not correlate with urinary thromboxane in deoxycorticosterone acetate–treated rats

Renal vascular resistance in deoxycorticosterone acetate (DOCA) salt–treated uninephrectomized rats is increased by high dietary chloride. Because DOCA salt–hypertensive rats exhibit an increased urinary excretion of thromboxane B2 (TXB2), a metabolite of thromboxane A2 (TXA2), the increased TXB2 excretion by DOCA salt–treated rats could relate to elevated dietary chloride, increased blood pressure, and/or the presence of intact renal tubules. We hypothesized that high NaCl intake, resulting in an elevated tubular chloride excretion, stimulates TXA2 production. A result of that production could be renal vasoconstriction. Baseline blood pressures were measured for 10 days, and then the rats were treated with DOCA (30 mg/kg) and fed (1) normal NaCl, (2) normal sodium with high chloride, or (3) high sodium chloride (NaCl) for 4.5 weeks. Next, the rats were uninephrectomized (1K) or unihydronephrectomized (1KHK) to yield one kidney without an intact tubular system and therefore no macula densa. Two and a half weeks later, urinary excretion of TXB2 was determined. DOCA-high NaCl-fed 1KHK or 1K rats had significant increases in systemic blood pressure to 172 ± 12 and 190 ± 5 mm Hg, respectively, compared with no significant increase in blood pressure among the other groups. Urinary TXB2 excretion was increased to 29 ± 4 pg per 24 hours per gram of body weight in all DOCA-treated 1KHK and 1K animals regardless of diet compared with DOCA-treated animals with two intact kidneys (13 ± 2 pg per 24 hours per gram of body weight). DOCA treatment in rats with one functional kidney results in the excretion of high levels of urinary TXB2 unrelated to dietary chloride load, blood pressure, or intact renal tubules. (J Lab Clin Med 2000;135:493-7)

RENAL GLOMERULAR RESPONSE TO THE INHIBITION OF PROSTAGLANDIN E2 SYNTHESIS AND PROTEIN LOADING AFTER THE RELIEF OF UNILATERAL URETEROPELVIC JUNCTION OBSTRUCTION

We investigated glomerular filtration rate and renal function reserve after the surgical relief of partial obstruction. We evaluated 4 boys and 1 girl 9 to 14 years old who underwent pyeloplasty because of unilateral ureteropelvic junction obstruction. Contralateral normal kidneys served as controls. The glomerular filtration rate (inulin clearance), and urinary excretion of prostaglandin E2, thromboxane B2 and endothelin were determined at baseline and after a meal of 4 gm./kg. cooked unsalted red meat on day 4 postoperatively. Tests were repeated the following day 1 hour after the oral administration of 20 mg./kg. aspirin, an inhibitor of prostaglandin E2 synthesis. Urine was collected separately through a bladder catheter and another catheter placed in the upper renal pelvis at surgery. Glomerular filtration rate at baseline was significantly greater in normal than in surgically treated kidneys (77.2 ml. per minute, range 60 to 98 versus 63.6, range 43 to 78, p = 0.04). Aspirin did not change baseline inulin clearance in normal kidneys but it significantly decreased the glomerular filtration rate in operated renal units (-4% versus -26.4%, p = 0.04). The concentration of all vasoactive compounds was not significantly different in the urine specimens of normal and operated kidneys. The administration of aspirin resulted in a significant decrease in mean urinary prostaglandin E2 excretion plus or minus standard error in operated but not in normal renal units (0.64+/-0.12 ng. per minute versus 0.27+/-0.06, p = 0.04). When expressed as mean versus baseline values, protein induced glomerular hyperfiltration seemed lower in operated than in contralateral intact kidneys (6.9% and 12.4%, respectively). In the immediate postoperative period previously obstructed kidneys maintain renal function via mechanisms that depend on the activation of prostaglandin, mimicking normal renal function. This effect is decreased by drugs that inhibit prostaglandin E2 production. Therefore, renal damage may be present when the glomerular filtration rate appears normal.

Low density lipoprotein apheresis therapy for steroid-resistant nephrotic syndrome

The pathogenic role of hyperlipidemia in long-standing nephrotic syndrome (NS) is known to be responsible for both the progression of glomerulosclerosis and tubulointerstitial injury, especially in focal segmental glomerulosclerosis (FGS). Aggressive lipid lowering treatment by low density lipoprotein (LDL) apheresis (LDL-A) using a dextran sulfate cellulose column to treat patients with steroid-resistant or frequently recurrent severe NS was performed first without fixing the protocol in eight patients with FGS and one with minimal change nephrotic syndrome (MCNS). The period of NS before LDL-A, number and average intervals of LDL-A until the end of the therapy, and the prognosis were investigated. Next, a multicenter study with a fixed protocol of LDL-A treatment was designed in combination with steroid therapy for treatment twice a week for three weeks and weekly for six weeks, and was performed in 17 patients with FGS. The effects on the state of NS in addition to the change of urinary eicosanoid metabolites and remission rates were evaluated. In the preliminary study, along with a rapid improvement of hyperlipidemia, a high incidence of remission was achieved by LDL-A performed at relatively short intervals. In the multicenter study with a fixed protocol, there was a significant decrease of urinary protein (P < 0.001) and increase of serum albumin (P < 0.02) as well as a decrease of thromboxane B2 (TXB2) excretion (P < 0.05) after the treatment. Urinary excretion of TXB2 was significantly reduced after LDL-A (P < 0.05). The rate of entering into complete or incomplete remission was 71% with a relatively short duration of nephrotic-range proteinuria using the LDL-A therapy in comparison with steroid therapy alone. The rapid improvement of hypercholesterolemia with LDL-A treatment may provide a new approach for a high rate of improvement in the degree of NS in steroid-resistant NS of FGS and MCNS.

Maternal Factors Modulate the Increase in Vasoactive Substances During Rat Pregnancy

Objective: To explore if the changes in vasoactive substances observed during early pregnancy in the rat are modulated by maternal or fetoplacental factors.Methods: Urinary excretion of cGMP, 6-keto-prostaglandin-Fla (6-keto-PGFla), thromboxane B2 and kallikrein activity was measured in pregnant (P, n= 11), pseudopregnant (PSP, n= 12), and virgin (n = 13) rats and in ovariec-tomized virgin rats supplemented with slow-release pellets containing either progesterone (50 mg/pellet) or estradiol (0.5 mg/pellet) or a combination of both hormones, for 21 days.Results: The cGMP excretion was higher in PSP rats than in virgin rats at day 5 (virgin = 82 ± 7, P = 93 ± 5, PSP = 110 ± 8 nmol/24 h,p < 0.05); at day 10, values were significantly increased in P and PSP rats. 6-keto-PGFla excretion was similarly elevated in P and PSP rats at day 5 (virgin = 120 ± 10, P = 160 ± 10, and PSP = 174 ± 14 ng/24 h,p < 0.01). This trend was still present at day 10. Thromboxane B2 excretion showed a nonsignificant increase in P and PSP rats in day 5; at day 10, values were significantly elevated in both experimental groups (virgin = 23 ± 2, P = 32 ± 4, and PSP = 32 ± 2 ng/24 h, p < 0.05). Kallikrein excretion was significantly increased in PSP and P rats at days 5 and 10. Estradiol or progesterone administration caused a significant decrease in serum aldosterone and an increase in urinary kallikrein activity.Conclusions: These results indicate that during the first half of rat pregnancy, the increment in vasoactive substances is modulated by maternal and not by fetoplacental factors.