thromboxane-a2 and Lupus-Nephritis

Topics: Animals; Disease Models, Animal; Glomerulonephritis; Lupus Nephritis; Rats; Thromboxane A2

In lupus nephritis (LN), renal thromboxane A2 (TXA2) production is increased, and inhibition of TXA2 activity improves renal function. In patients with LN, renal function depends very much on vasodilatory prostaglandins, and indeed inhibiting the prostaglandin-forming enzyme cyclooxygenase (COX) with aspirin or related compounds was detrimental on renal hemodynamics in these patients. There are no data so far on whether the excessive TXA2 production in LN derives from upregulation of type I or type II isoforms of COX. It was found that TXB2 synthesis and COX-2 gene expression were higher in peripheral blood mononuclear cells from patients with active LN compared to patients in the inactive form of the disease and to healthy subjects. Unlike COX-2, levels of COX-1 mRNA were comparable in lupus patients and control subjects and were not influenced by the disease activity. Immunoperoxidase studies on kidney biopsies showed COX-1 staining in glomerular arterioles and other renal vessels, with no evident difference between lupus biopsies and control specimens taken from either individuals who were free of renal disease or patients with non-lupus nephropathies. In contrast, COX-2 staining was definitely stronger in specimens from patients with active LN than control specimens. In active LN, COX-2-specific staining was localized mainly in the glomeruli, with a weaker signal on tubuli and in the interstitium. Double-staining studies with an antibody against the macrophage marker CD68 and an anti-COX-2 antibody definitely showed that COX-2 and CD68 often colocalized on the same cell, with only occasional glomerular COX-2-stained mesangial areas. Patients with non-lupus nephropathies had no increase in renal COX-2 expression. These results indicate that COX-2 upregulation is a specific finding of active LN and that monocytes infiltrating the glomeruli contribute to the exaggerated local synthesis of TXA2. If this is correct, COX-2 may soon become a target for therapeutic intervention in this disease.

Topics: Adult; Biopsy; Cyclooxygenase 2; Electron Transport Complex IV; Female; Gene Expression; Humans; Immunohistochemistry; Isoenzymes; Kidney; Leukocytes, Mononuclear; Lupus Nephritis; Male; Membrane Proteins; Middle Aged; Prostaglandin-Endoperoxide Synthases; Radioimmunoassay; Reference Values; RNA; Steroids; Thromboxane A2; Up-Regulation

To examine abnormalities of prostanoid metabolism in lupus nephritis, which may affect renal function, and the effects of 4 day dosing of a selective thromboxane A2 (TXA2) synthetase inhibitor, DP-1904, on prostanoid metabolism.. Urinary levels of various prostanoids, thromboxane B2(TXB2), 11-dehydro-TXB2, 6-keto-prostaglandin F1 alpha, 2,3-dinor-6-keto-PGF1 alpha, and prostaglandin E2 were determined. In a randomized crossover study, 8 patients with biopsy proven lupus nephritis were given 4 days' oral administration of DP-1904 (400 mg/day bid) or indomethacin (50 mg/day bid). The effects of DP-1904 on prostanoid metabolism were studied.. Urinary excretion of TXB2, which reflects the renal production of TXA2, was significantly increased in patients with lupus nephritis compared with non-renal systemic lupus erythematosus (SLE)(p < 0.05); enhanced production of TXA2 was also estimated in patients with lupus nephritis. The urinary TXB2/6-keto-PGF1 alpha ratio was also increased in lupus nephritis compared with non-renal SLE (p < 0.01), indicating a prostanoid imbalance that may lead to impaired renal function and subsequent pathology. During administration of DP-1904, the urinary excretion of TXB2 was significantly decreased after 1 to 2 days. An increase in creatinine clearance as a measure of renal function was observed. In contrast, during the administration of indomethacin, urinary excretion of both TXB2 and 6-keto-PGF1 alpha decreased and there were no significant changes in the urinary TXB2/6-keto-PGF1 alpha ratio or creatinine clearance. Hemodynamic changes were associated with a slight increase in sodium excretion, but with no change in arterial blood pressure. No side effects were elicited during the 4 days of treatments.. The abnormal prostanoid metabolism observed in lupus nephritis could aggravate renal function, which was mediated hemodynamically, and the altered metabolism was reversible and at least partially corrected by a TXA2 synthetase inhibitor, DP-1904.

Topics: Adult; Enzyme Inhibitors; Female; Humans; Imidazoles; Indomethacin; Kidney; Lupus Nephritis; Middle Aged; Prostaglandins; Tetrahydronaphthalenes; Thromboxane A2; Thromboxane-A Synthase

To test the hypothesis that the vasoconstrictor thromboxane A2 may affect renal hemodynamics in lupus nephritis, we examined the short-term effects of a selective thromboxane-receptor antagonist, BM 13,177, and of low-dose aspirin. In a randomized, double-blind, crossover study, 10 patients with biopsy-proved lupus nephritis were given a 48-hour continuous infusion of BM 13,177 or placebo. At base line, seven patients had markedly elevated urinary levels of thromboxane B2, the breakdown product of thromboxane A2. During the infusion of BM 13,177, the inulin clearance rate, which was 68 ml per minute per 1.73 m2 of body-surface area at base line, increased by an average of 24 percent (range, 12 to 47 percent; P less than 0.01). Para-aminohippurate clearance was increased to the same extent, with no change in the filtration fraction. The bleeding time doubled, indicating an occupancy of platelet thromboxane receptors of more than 95 percent. The hemodynamic changes were associated with a significant increase in sodium excretion from 76 to 118 mmol per day (P less than 0.01) but with no change in arterial blood pressure. In another study, 10 additional patients with lupus nephritis were randomly assigned to receive either placebo or 20 mg of aspirin twice daily for four weeks. The aspirin regimen produced a selective, cumulative inhibition of platelet cyclooxygenase activity and a doubling of bleeding time. However, there was no change in the inulin clearance rate and no change in urinary levels of thromboxane B2 or 6-keto-prostaglandin F1 alpha, which are indicators of renal synthesis of thromboxane A2 and prostacyclin, respectively. We conclude that in lupus nephritis, impairment of renal function is at least in part mediated hemodynamically and is reversible with a thromboxane antagonist. Platelets, however, are not a major source of thromboxane A2 synthesis and action within the kidney.

Topics: Adolescent; Adult; Aged; Aspirin; Clinical Trials as Topic; Double-Blind Method; Female; Humans; Kidney; Lupus Nephritis; Male; Middle Aged; Random Allocation; Renal Circulation; Sulfonamides; Thromboxane A2

Proliferative lupus nephritis (LN) is marked by increased renal thromboxane (TX) A₂ production. Targeting the TXA₂ receptor or TXA₂ synthase effectively improves renal function in humans with LN and improves glomerular pathology in murine LN. This study was designed to address the following hypotheses: (1) TXA₂ production in the MRL/MpJ-Tnfrsf6(lpr)/J (MRL/lpr) model of proliferative LN is cyclooxygenase (COX)-2 dependent and (2) COX2 inhibitor therapy improves glomerular filtration rate (GFR), proteinuria, markers of innate immune response and glomerular pathology.. Twenty female MRL/lpr and 20 BALB/cJ mice were divided into 2 equal treatment groups: (1) SC-236, a moderately selective COX2 inhibitor or (2) vehicle. After treatment from the age of 10 to 20 weeks, the effectiveness of inhibition of TXA₂ was determined by measuring urine TXB₂. Response endpoints measured at the age of 20 weeks were renal function (GFR), proteinuria, urine nitrate + nitrite (NO(x)) and glomerular histopathology.. SC-236 therapy reduced surrogate markers of renal TXA₂ production during early, active glomerulonephritis. When this pharmacodynamic endpoint was reached, therapy improved GFR. Parallel reductions in markers of the innate immune response (urine NO(x)) during therapy were observed. However, the beneficial effect of SC-236 therapy on GFR was only transient, and renal histopathology was not improved in late disease.. These data demonstrate that renal TXA2 production is COX2 dependent in murine LN and suggest that NO production is directly or indirectly COX2 dependent. However, COX2 inhibitor therapy in this model failed to improve renal pathology, making COX2 inhibition a less attractive approach for treating LN.

Topics: Animals; Cyclooxygenase 2 Inhibitors; Female; Glomerular Filtration Rate; Kidney; Lupus Nephritis; Mice; Mice, Inbred BALB C; Mice, Inbred MRL lpr; Nitrates; Nitric Oxide; Nitrites; Pyrazoles; Sulfonamides; Thromboxane A2; Thromboxane B2

To examine the role of immune complexes in the prostanoid metabolism of glomerular capillary endothelial cells (EC) and platelets in lupus nephritis. Heat aggregated IgG (HA-IgG), instead of immune complexes, was incubated using an in vitro coculture system with human umbilical vein EC, instead of glomerular capillary EC, and platelets. The effect of complement component C1q and a novel imidazole-type thromboxane A2 (TXA2) synthetase inhibitor, DP-1904, on this prostanoid metabolism change was also investigated.. EC monolayers (1.5x10(5) cells/well) were incubated with various concentrations of HA-IgG, monomeric IgG, or medium alone for 1 h at 37 degrees C, and then incubated with platelet suspensions (1x10(8) cells/ml) for various times. Concentrations of TXB2 and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), the stable hydrolysis products of TXA2 and prostaglandin I2 (PGI2), respectively, released in the supernatants were measured by ELISA.. HA-IgG bound to EC monolayers produced TXB2 and 6-keto-PGF(1alpha) in a concentration dependent manner and much more than monomeric IgG or medium alone did. However, the production of 6-keto-PGF(1alpha) stimulated with HA-IgG was much lower than that of TXB2, indicating a large imbalance between TXA2 and PGI2. Preincubation of HA-IgG with purified C1q partially suppressed the production of TXB2, but not that of 6-keto-PGF(1alpha). DP-1904 suppressed the production of TXB2 completely, but by sharp contrast, it dramatically increased the production of 6-keto-PGF(1alpha) from EC and platelets by HA-IgG.. The large imbalance of TXA2 and PGI2 produced by the interaction of EC, immune complexes, and platelets may be associated with alterations in glomerular pathological findings and hemodynamics mediated by immune complexes in lupus nephritis. C1q and a TXA2 synthetase inhibitor may improve the abnormal prostanoid metabolism change of lupus nephritis.

Topics: Antigen-Antibody Complex; Blood Platelets; Cells, Cultured; Coculture Techniques; Complement C1q; Endothelium, Vascular; Epoprostenol; Hot Temperature; Humans; Imidazoles; Immunoglobulin G; Infant, Newborn; Lupus Nephritis; Male; Tetrahydronaphthalenes; Thromboxane A2; Thromboxane-A Synthase

Matrix degradation products such as fragmented hyaluronan (HA) display important proinflammatory effects on renal tubular epithelial cells (TECs) and macrophages (MPhis). We hypothesized that HA could up-regulate cyclooxygenase type 2 (COX-2) in these cells and that the subsequent production of thromboxane A2 (TXA2) could play a role in inflammatory renal lesions.. We used an in vitro approach to examine the expression of COX-1 and COX-2 and the production of TXA2 in response to fragments of HA. COX-2 mRNA, protein, and the resulting TXA2 production were measured in CD44-positive, HA-responsive cells lines of TECs and MPhi. COX-2 mRNA was also measured in vivo in MRL-Faslpr mice and in mice with anti-glomerular basement membrane (anti-GBM) nephritis.. In TECs and MPhis, HA increased the steady-state COX-2 mRNA and protein levels markedly, whereas COX-1 mRNA levels did not change. The HA-induced response was comparable to lipopolysaccharide stimulation. In comparison with MPhi, the response was much weaker in TECs. Likewise, the production of TXA2 in response to HA was markedly increased in MPhi, but less in TECs. In TECs and in MPhi, the HA-stimulated TXA2 synthesis was inhibited with the COX-2-selective inhibitors SC58125 (12.5 micromol/L) or celecoxib (0.25 to 5.00 micromol/L). COX-2 mRNA levels were increased in nephritic mice with MRL-Faslpr lupus nephritis and in mice with anti-GBM disease.. HA is a proinflammatory factor that stimulates COX-2 expression and subsequent TXA2 production. Since HA accumulates markedly in renal injury, we speculate that this matrix molecule could therefore play a significant role in thromboxane-mediated immune events in the kidney.

Topics: Animals; Anti-Glomerular Basement Membrane Disease; Cell Line; Cyclooxygenase 2; Hyaluronic Acid; Isoenzymes; Kidney; Kidney Tubules; Lupus Nephritis; Macrophages; Mice; Prostaglandin-Endoperoxide Synthases; RNA, Messenger; Thromboxane A2; Thromboxane-A Synthase

Recently, it has been demonstrated that the production of prostaglandins and thromboxane is increased in patients with chronic glomerulonephritis and lupus nephritis. We recently demonstrated that thromboxane A(2) delayed the clearance of heat-aggregated bovine serum albumin deposited in glomeruli. In the present study, we investigated the effect of thromboxane A(2) on the clearance of macromolecules in nephritic glomeruli. First, we attempted to clarify the conditions for the clearance of heat-aggregated bovine serum albumin in nephritic glomeruli, using glomeruli isolated from control and anti-glomerular basement membrane nephritic mice. Heat-aggregated bovine serum albumin was injected twice into each mouse. The glomeruli were then isolated and incubated in culture medium. The heat-aggregated bovine serum albumin content of control glomeruli gradually diminished with incubation time up to 24 h. The heat-aggregated bovine serum albumin content of nephritic glomeruli was 69% higher than that of control glomeruli at 24 h incubation. The production of thromboxane B(2) (the stable metabolite of thromboxane A(2)) in nephritic glomeruli showed about a sevenfold increase compared with control. DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydro-naphthalene-2-carboxylic acid hydrochloride], a thromboxane A(2) synthase inhibitor, and KT2-962 [sodium 3-(4-(4-chlorophenyl-butylsulfonamido) butyl)-6-isopropylazulene-1-sulfonate], a selective thromboxane A(2) receptor antagonist, significantly reduced the heat-aggregated bovine serum albumin content in nephritic glomeruli. Normal glomeruli treated with U-46619 [15S-hydroxy-11a,9a-(epoxymethano)prosta-5Z,13E-dienoic acid], a stable analogue of thromboxane A(2), had significantly more heat-aggregated bovine serum albumin than control glomeruli. We next investigated whether thromboxane A(2) could affect the uptake/disposal of heat-aggregated bovine serum albumin by cultured rat mesangial cells. U-46619 significantly enhanced the uptake and inhibited the disposal of heat-aggregated bovine serum albumin by mesangial cells. Finally, we performed experiments to elucidate the role of the thromboxane A(2) receptor (TP receptor) in the clearance of heat-aggregated bovine serum albumin using TP-deficient mice. The glomerular heat-aggregated bovine serum albumin content of TP-receptor knockout [TP(-/-)] mice was lower than that of wild-type [WT(+/+)] mice. U-46619 dose dependently increased the uptake of heat-aggregated bovine s

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Antibodies; Autoantibodies; Benzenesulfonates; Cells, Cultured; Cycloheptanes; Enzyme Inhibitors; Glomerular Mesangium; Hot Temperature; Imidazoles; Kidney Glomerulus; Lupus Nephritis; Male; Mice; Mice, Inbred ICR; Mice, Knockout; Nephritis; Receptors, Thromboxane; Serum Albumin, Bovine; Tetrahydronaphthalenes; Thromboxane A2; Thromboxane-A Synthase; Vasoconstrictor Agents

We examined the effect of KW-3635, a specific thromboxane A2 (TXA2)-receptor antagonist, on the development of lupus nephritis in NZB x NZW F1 mice. KW-3635 was orally given once a day for 33 weeks beginning at eight weeks of age. In the control group, the mice began to die at 39 weeks of age, showing severe proteinuria and histopathologic abnormality in the renal glomeruli. Administration of KW-3635 (30 mg/kg/day) significantly reduced urinary protein excretion (1.7 +/- 0.9 vs. 8.5 +/- 2.4 mg/6 hr/mouse, P < 0.01), mortality (1/18 vs. 6/19, P < 0.05) and the histopathologic score of the kidney examined at 41 weeks of age. Thus, chronic administration of KW-3635 markedly attenuated the renal disease in NZB x NZW F1 mice, suggesting that TXA2 is an important mediator of the pathogenesis in this murine model of lupus nephritis.

Topics: Administration, Oral; Animals; Antibodies, Antinuclear; Benzimidazoles; Benzoxepins; Female; Immunohistochemistry; Kidney; Lupus Nephritis; Mice; Proteinuria; Thromboxane A2

To investigate the role of thromboxane A2 (TxA2) in murine lupus, we assessed the effects of the specific thromboxane receptor antagonist GR32191 on immune complex glomerulonephritis in MRL-lpr/lpr mice. Forty mg/kg/day GR32191 was given by twice daily subcutaneous injection for eight weeks beginning at 12 weeks of age. This dose completely blocked the renal vasoconstriction produced by the thromboxane agonist U46619. After eight weeks of treatment, both glomerular filtration rate (GFR) (8.9 +/- 0.6 vs. 6.8 +/- 1.1 ml/min/kg; P less than 0.05) and PAH clearance (CPAH) (37.4 +/- 2.5 vs. 29.9 +/- 3.3 ml/min/kg; P less than 0.05) were significantly higher in mice given GR32191 compared to vehicle treated animals. Administration of GR32191 also reduced proteinuria from 18.1 +/- 11.6 to 3.7 +/- 1.3 mg/24 hours (P less than 0.05). In GR32191 treated MRL-lpr/lpr mice, renal hemodynamic function and proteinuria were not significantly different from congenic MRL-+/+ controls. Thromboxane receptor blockade had striking affects on renal histomorphology reducing both hyaline thrombi in glomeruli (P = 0.022) and interstitial inflammation (P = 0.006). Glomerular crescents and severity of vasculitis also tended to be reduced in mice receiving the thromboxane receptor antagonist. The overall histopathologic score in mice given GR32191 was significantly lower than vehicle treated animals (4.7 +/- 0.5 vs. 8.4 +/- 1.5; P = 0.016). These effects of GR32191 were associated with decreased excretion of thromboxane B2 (TxB2) in urine (292 +/- 37 vs. 747 +/- 155 pg/24 hr; P less than 0.005) as well as a modest reduction in glomerular deposits of IgG (semiquantitative score 2.6 +/- 0.2 vs. 3.5 +/- 0.2; P less than 0.02). Thus, chronic thromboxane receptor blockade markedly altered the course of renal disease in MRL-lpr/lpr mice, suggesting that TxA2 is an important mediator of renal dysfunction and injury in this murine model of lupus nephritis.

Topics: Animals; Antibodies, Antinuclear; Biphenyl Compounds; DNA; Hemodynamics; Heptanoic Acids; Immunoglobulins; Interleukin-1; Kidney; Lupus Nephritis; Mice; Mice, Mutant Strains; Receptors, Prostaglandin; Receptors, Thromboxane; RNA, Messenger; Thromboxane A2

To investigate the physiologic significance of enhanced renal thromboxane production in murine lupus nephritis, we measured renal hemodynamics and eicosanoid production in MRL-lpr/lpr mice from 8 to 20 weeks of age. Over this age range, MRL-lpr/lpr mice develop an autoimmune disease with nephritis similar to human systemic lupus erythematosus (SLE). In these studies, glomerular filtration rate (GFR) and PAH clearance (CPAH) decreased progressively with age in MRL-lpr/lpr mice, but not in controls. This impairment of renal hemodynamics was associated with increased renal thromboxane production, as well as increased excretion of both thromboxane B2 (TxB2) and 2,3-dinor TxB2 in urine. There was an inverse correlation between renal thromboxane production in MRL-lpr/lpr mice and both GFR and CPAH. Furthermore, there were positive correlations between thromboxane production by the kidney and both the severity of renal histopathology and serum anti-DNA antibody levels measured in individual animals. Enhanced urinary excretion of TxB2 and the development of renal dysfunction also coincided temporally with the appearance of increased levels of interleukin 1 beta (IL-1 beta) mRNA in renal cortex. Acute administration of the specific thromboxane receptor antagonist GR32191 to MRL-lpr/lpr mice restored GFR to normal in early stages of the autoimmune disease. However, in animals with more advanced nephritis, the effect of acute thromboxane receptor blockade on renal hemodynamics was less marked. We conclude that thromboxane A2 is an important mediator of reversible renal hemodynamic impairment in murine lupus, especially in the early phase of disease.

Topics: Age Factors; Animals; Biphenyl Compounds; Blotting, Northern; DNA; Heptanoic Acids; Interleukin-1; Kidney; Kidney Function Tests; Lupus Nephritis; Metabolic Clearance Rate; Mice; Mice, Inbred Strains; Radioimmunoassay; RNA, Messenger; Thromboxane A2; Thromboxane B2

Topics: Arachidonic Acid; Arachidonic Acids; Arginine Vasopressin; Calcium; Cells, Cultured; Glomerular Filtration Rate; Humans; Imino Acids; In Vitro Techniques; Ionomycin; Kidney; Lupus Nephritis; Membrane Potentials; Muscle, Smooth; Potassium Chloride; Receptors, Prostaglandin; Receptors, Thromboxane; Renal Circulation; Spectrometry, Fluorescence; Thromboxane A2