Antiproteinuric effect of a thromboxane receptor antagonist, S-1452, on rat diabetic nephropathy and murine lupus nephritis

Effect of pharmaceutical interventions targeting thromboxane receptors and thromboxane synthase in cardiovascular and renal diseases

The present review focuses on the roles of thromboxane A2 (TxA2) in arterial thrombosis, atherogenesis, vascular stent-related ischemic events and renal proteinuria. Particular emphasis is laid on therapeutic interventions targeting the TxA2 (TP) receptors and TxA2 synthase (TS), including dual TP-receptor antagonists and TS inhibitors. Their significant inhibitory efficacies on arterial thrombogenesis, atherogenesis, restenosis after stent placement, vasoconstriction and proteinuria indicate novel and improved treatments for cardiovascular and selected renal diseases. New therapeutic interventions of the TxA2 pathway may also be beneficial for patients with poor biological antiplatelet drug response, for example, to aspirin and/or clopidogrel. These new TP/TS agents offer novel improved treatments to efficiently and simultaneously interfere with thrombogenesis and atherogenesis, and to enlarge the existing panel of platelet inhibitors for efficient prophylaxis and treatment of arterial thrombosis and renal proteinuria.

Synthesis and biological evaluation of sulfonylurea and thiourea derivatives substituted with benzenesulfonamide groups as potential hypoglycemic agents

A novel class of sulfonylurea and thiourea derivatives substituted with benzenesulfonamide groups were designed and synthesized. The target compounds were assayed for the effects on the insulin release of isolated rat pancreatic islets and the glucose transport in adipocytes of rats. Some of them exhibited high potency. Compound 10 also had potent antiplatelet activity and showed an excellent property to protect collagen-epinephrine-induced mice mortality as well as plasma glucose-lowering activity in vivo. The preliminary pharmacological profile of compound 10 showed that it might be useful in the treatment of diabetics with cardiovascular and nephropathy complications.

A role for the thromboxane receptor in L-NAME hypertension

Actions of the lipid mediator thromboxane (Tx) A2 acting through the TP receptor contribute to the pathogenesis of cardiovascular disease. To further explore the role of TxA2 in hypertension, we examined the consequences of deficiency of the TP receptor on the course of hypertension associated with endothelial dysfunction and salt sensitivity. To this end, the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was administered to TP-deficient (Tp-/-) and wild-type (Tp+/+) control mice in drinking water for 21 wk along with a high-salt (HS; 6% NaCl) diet. Administration of L-NAME increased urinary excretion of TxB2 to a similar extent in both Tp+/+ and Tp-/- animals. L-NAME also caused significant and sustained elevations in blood pressure that reached a maximum between weeks 3 and 6. However, the severity of hypertension was attenuated in the Tp-/- mice throughout the study period (P<0.001). At the end of the study, the wild-type mice developed significant cardiac hypertrophy (23.6+/-2% increase in heart-to-body weight ratio). The severity of cardiac hypertrophy was attenuated in the TP-deficient group (11.1+/-2.6%; P<0.05). In contrast, kidney hypertrophy was exaggerated in the Tp-/- mice compared with controls (37.1+/-5.4 vs. 12.3+/-2.3%; P<0.01). Moreover, the severity of glomerulosclerosis, tubule vacuolization, and interstitial chronic inflammation was also enhanced in the Tp-/- group (P<0.01). Thus, in L-NAME hypertension, TP receptors contribute to elevated blood pressure and cardiac hypertrophy. In this model, TP receptors also provided unexpected protection against kidney injury.

High rabdosiin and rosmarinic acid production in Eritrichium sericeum callus cultures and the effect of the calli on masugi-nephritis in rats

During an investigation of plant cell cultures that might be useful in the treatment of renal disorders, we established a vigorously-growing E-4 callus culture of Eritrichium sericeum that produced large amounts of caffeic acid metabolites, (-)-rabdosiin (1.8% dry wt) and rosmarinic acid (4.6% dry wt). Elicitation of the calli by methyl jasmonate induced a 38% increase in total polyphenol production. The most efficient method of eliciting (-)-rabdosiin biosynthesis was through the treatment of E-4 calli with cuprum glycerate, which induced an increase in (-)-rabdosiin production of as much as 4.1% dry wt. Oral administration of E-4 callus biomass (100 mg/kg/d for 30 d) to rats with induced Masugi-nephritis caused an increase in diuresis and lowered creatinine excretion and proteinuria levels as compared with Masugi-nephritis untreated rats. While all of the Masugi-nephritis untreated rats began to suffer, near a quarter of the E-4 treated rats remained in good health. This result indicates that the E-4 culture has the potential to alleviate the symptoms associated with nephritis.

Renal effects of S18886 (Terutroban), a TP receptor antagonist, in an experimental model of type 2 diabetes

Thromboxane A(2) (TxA(2)) is assumed to contribute to the development of diabetes complications, including nephropathy. We investigated whether the selective thromboxane-prostanoid endoperoxide receptor antagonist, S18886, ameliorates renal damage in uninephrectomized (UNX) obese Zucker rats (OZR). S18886, at doses of 10 (S18886-10) and 30 (S18886-30) mg x kg(-1) x day(-1), was administered to UNX-OZR by gavage over 8 weeks (n = 8 each group). UNX lean rats (n = 12) and OZR rats that received placebo (OZR-PLAC, n = 8) served as controls. As compared with the OZR-PLAC, S18886 had no significant effect on the elevated blood pressure and the enhanced creatinine clearance, while augmented proteinuria was partially prevented (-12 and -37%, low and high dose, respectively; NS). The increased excretion of transforming growth factor beta(1) (TGF-beta(1)) and of the thromboxane metabolite 2,3-dinor thromboxane B(2) (TxB(2)) was lowered (P < 0.05). S18886 prevented both the enhanced mesangiolysis (P < 0.01) in the OZR-PLAC as well as enlargement and degeneration of podocytes. In the blood, S18886-30 augmented the antioxidant enzymes (P < 0.01) and lessened the increase of plasma advanced oxidation protein products (-25%, NS). Body weight, hyperglycemia, and dyslipidemia remained uninfluenced under both doses of treatment. S18886 has renoprotective properties in the model of UNX-OZR. It prevents mesangiolysis, reduces urinary TGF-beta(1) and 2,3-dinor-TxB(2) excretion, and enhances the antioxidative defense.

15-deoxy Delta12,14-prostaglandin J2 suppresses transcription by promoter 3 of the human thromboxane A2 receptor gene through peroxisome proliferator-activated receptor gamma in human erythroleukemia cells

In humans, thromboxane (TX) A2 signals through two receptor isoforms, thromboxane receptor (TP)alpha and TPbeta, which are transcriptionally regulated by distinct promoters, Prm1 and Prm3, respectively, within the single TP gene. The aim of the current study was to investigate the ability of the endogenous peroxisome proliferator-activated receptor (PPAR)gamma ligand 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) to regulate expression of the human TP gene and to ascertain its potential effects on the individual TPalpha and TPbeta isoforms. 15d-PGJ2 suppressed Prm3 transcriptional activity and TPbeta mRNA expression in the platelet progenitor megakaryocytic human erythroleukemia (HEL) 92.1.7 cell line but had no effect on Prm1 or Prm2 activity or on TPalpha mRNA expression. 15d-PGJ2 also resulted in reductions in the overall level of TP protein expression and TP-mediated intracellular calcium mobilization in HEL cells. 15d-PGJ2 suppression of Prm3 transcriptional activity and TPbeta mRNA expression was found to occur through a novel mechanism involving direct binding of PPARgamma-retinoic acid X receptor (RXR) heterodimers to a PPARgamma response element (PPRE) composed of two imperfect hexameric direct repeat (DR) sequences centred at -159 and -148, respectively, spaced by five nucleotides (DR5). These data provide direct evidence for the role of PPARgamma in the regulation of human TP gene expression within the vasculature and point to further critical differences in the modes of transcriptional regulation of TPalpha and TPbeta in humans. Moreover, these data highlight a further link between enhanced risk of cardiovascular disease in diabetes mellitus associated with increased synthesis and action of thromboxane A2 (TXA2).

Agents in development for the treatment of diabetic nephropathy

Diabetic nephropathy is a leading cause of end-stage renal disease, and accounts for significant morbidity and mortality in patients with diabetes. Diabetic nephropathy seems to occur as a result of an interaction between metabolic and haemodynamic factors, which activate common pathways that lead to renal damage. In the past, the treatment of diabetic nephropathy has focused on the control of hyperglycaemia. Newer targets, some of which are linked to glucose-dependent pathways, appear to be a major focus of new treatments directed against the development and progression of renal damage as a result of diabetes. It is anticipated that additional therapeutic approaches that inhibit both metabolic and haemodynamic pathways will include strategies that target growth factors, cytokines and intracellular second messengers. Such an approach is expected to lead to improved therapies for the treatment of diabetic nephropathy.

Anti-DNA autoantibodies and systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that affects most of the organs and tissues of the body, causing glomerulonephritis, arthritis, and cerebritis. SLE can be fatal with nephritis, in particular, predicting a poor outcome for patients. In this review, we highlight what has been learned about SLE from the study of mouse models, and pay particular attention to anti-DNA autoantibodies, both as pathological agents of lupus nephritis and as DNA-binding proteins. We summarize the current approaches used to treat SLE and discuss the targeting of anti-DNA autoantibodies as a new treatment for lupus nephritis.

Thromboxane receptors in human kidney tissues

Thromboxane (TX) A2 effects in the kidneys include contraction of glomerular mesangial cells and intrarenal vascular tissue. A kidney cDNA encoding a TX receptor expressed in rat renal glomeruli and rat renal arterial smooth muscle cells has been reported. However, TXA2 receptors in human kidneys have not been documented. The purpose of this study was to identify and characterize TXA2 receptors in glomeruli and intrarenal arteries isolated from human kidneys. Normal kidneys, not used for transplant because of technical reasons, were kept at -70 degrees C and used for research purposes. The glomeruli and intrarenal arteries were isolated from renal cortical tissue by a mechanical sieving technique. The equilibrium dissociation constant and receptor number were determined by nonlinear analysis of binding inhibition data. The data were generated in radioreceptor assays using [125I]-BOP, a stable analog of TXA2. The dissociation constants (mean +/- SEM) for binding of I-BOP to human glomeruli and intrarenal arterial membranes were 6.6 +/- 1.1 nM (n = 7) and 20 +/- 6 nM (n = 7), respectively (p < 0.05). The receptor number was 311 +/- 91 fmol/mg protein (n = 7) in glomeruli and 74 +/- 16 fmol/mg protein (n = 7) in intrarenal arterial membranes (p < 0.04). The order of specificity of TXA2 analogs for [125I]-BOP binding sites was similar in glomeruli and in arterial membranes and was I-BOP > or = U46619 > or = pinane TXA2 > or = carbocyclic TXA2 > or = PGH2. These findings provide direct evidence for the presence of specific, high-affinity [125I]-BOP binding sites in human renal glomeruli and extraglomerular vascular tissue. These data also indicate that the human binding sites have higher affinity for the TXA2 agonist I-BOP than for PGH2.

Novel approaches in the treatment of lupus nephritis

Lupus nephritis can be managed successfully in the majority of cases; most therapies, however, are associated with significant side-effects. Several new agents aiming at specific stages in the pathogenesis of lupus are in different phases of clinical trials. The central role of lymphocytes makes them targets of various therapeutic approaches. Lymphocyte depletion can be achieved by high-dose chemotherapy with or without bone marrow transplantation. Nucleoside analogs selectively deplete mononuclear cells; antibodies against T or B cell surface antigens target specific subsets of lymphocytes. Synchronized plasmapheresis has been used in an attempt to delete pathogenic lymphocyte clones activated by plasmapheresis. Treating patients with DNase or neutralizing pathogenic antibodies by administering specific binding peptides or inducing specific anti-idiotype antibodies may prevent immune complex formation and/or deposition. Blocking the complement cascade or some of the inflammatory mediators like thromboxane A2 may be efficacious even if immune complex deposition could not be prevented. Inducing antigen-specific tolerance or interfering with important interactions between T-lymphocytes and other cells by blocking CD40 ligand or decreasing the level of interleukin-10 are some of the other approaches currently under clinical investigation.

Role of thromboxane A2, endothelin-1 and endothelin-3 in rat nephrotoxic serum nephritis

To clarify the role of thromboxane A2 (TxA2), endothelin-1 (ET-1) and endothelin-3 (ET-3) in the progression of glomerular injury in accelerated nephrotoxic serum nephritis (NTN) in the rat, we studied the expression of ET-1 and ET-3 at the kidney by immunohistochemical method and examined the effect of a novel TxA2 receptor antagonist, S-1452. The S-1452-treated group showed significantly lowered 24-hr proteinuria and milder glomerular cell proliferation and lobulation than the non-treated group (NT group) on experimental day 10. There was no significant difference in the glomerular polymorphonuclear cell (PMN) exudation between the 2 groups. Immunofluorescent findings revealed that ET-1 and ET-3 were seen along the glomerular capillary wall and partly in the mesangial area in all rats of the NTN group. The degree and positive rate of ET-1 and ET-3 staining were significantly higher in the NTN group than in the S-1452 group. These findings suggest that TxA2 may be an important mediator in the development of NTN, and that TxA2 receptor antagonist may be useful for the reduction of glomerular injury in this type of nephritis. In addition, local production of ET may contribute to the development of this nephritis.