Abnormal prostanoid metabolism in lupus nephritis and the effects of a thromboxane A2 synthetase inhibitor, DP-1904

Bioactive Lipids in Age-Related Disorders

Our own studies and those of others have shown that defects in essential fatty acid (EFA) metabolism occurs in age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, immune dysfunction and cancer. It has been noted that in all these disorders there could occur a defect in the activities of desaturases, cyclo-oxygenase (COX), and lipoxygenase (LOX) enzymes leading to a decrease in the formation of their long-chain products gamma-linolenic acid (GLA), arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). This leads to an increase in the production of pro-inflammatory prostaglandin E2 (PGE2), thromboxanes (TXs), and leukotrienes (LTs) and a decrease in anti-inflammatory lipoxin A4, resolvins, protectins and maresins. All these bioactive molecules are termed as bioactive lipids (BALs). This imbalance in the metabolites of EFAs leads to low-grade systemic inflammation and at times acute inflammatory events at specific local sites that trigger the development of various age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, coronary heart disease, atherosclerosis, and immune dysfunction as seen in rheumatoid arthritis, lupus, nephritis and other localized inflammatory conditions. This evidence implies that methods designed to restore BALs to normal can prevent age-related disorders and enhance longevity and health.

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 (TXB2) and 2,3-dinor 6-ketoPGF1α (PGI-M), the stable metabolites of thromboxane A2 and prostacyclin, respectively, in 74 patients with SLE and 70 controls. In subjects who were not receiving aspirin, TXB2 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, TXB2 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 TXB2 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. Lupus (2007) 16, 981—986.

Prognostic Value of Renal Hemodynamic Characteristics in Patients with Proliferative Lupus Nephritis

BACKGROUND/AIM

Previous studies showed that renal hemodynamic parameters, especially the filtration fraction (FF), are decreased in patients with active lupus nephritis (LN). In this study, we evaluate the prognostic value of renal hemodynamic function tests on the renal outcome in patients with proliferative LN.

METHODS

We performed a retrospective cohort study of our patients with proliferative LN from 1986 to 2005. Glomerular filtration rate (GFR) and FF before treatment were measured. Treatment failure was defined as a renal relapse or development of end-stage renal disease.

RESULTS

Thirty-seven patients were included. The median follow-up period was 8 years. Creatinine clearance, GFR, and FF before treatment correlated with the creatinine clearance at the end of follow-up (p = 0.001, p = 0.006, and p = 0.04, respectively). The FF was decreased in 92% of our patients, but FF and GFR did not have a prognostic value with regard to treatment failure.

CONCLUSIONS

Most patients with proliferative LN had a low FF. Low GFR and FF at baseline were correlated with a worse renal function at the end of follow-up, but this had no prognostic value in individual patients.

Captopril effect on prostaglandin E2, thromboxane B2 and proteinuria in lupus nephritis patients

OBJECTIVE

High urinary Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) levels have been reported in lupus nephritis (LN). Captopril diminishes proteinuria and improves glomerular filtration rate (GFR), and may have effect on immune function. We evaluate captopril effect on urinary PGE2, and TxB2.

METHODS

Eighteen LN patients were randomly assigned to two groups. Group 1 received only prednisone plus cyclophosphamide. Group 2 received also captopril. Serum creatinine, GFR, RPF, urinary proteins, PGE2 and TxB2, were assessed.

RESULTS

There were no differences between the initial and final assessments in Group 1. Group 2 showed a significant decrement in proteinuria (p=0.003) and serum creatinine (p=0.01) at the end of the study. PGE2 decreased significantly when compared with the initial value (p=0.02).

CONCLUSION

Captopril plus usual treatment, improved serum creatinine and decreased proteinuria in parallel with prostaglandin E2 reduction. This effect is not related to changes in GFR or RPF. Captopril may have an immunomodulatory effect on local inflammatory processes in lupus nephritis.

A pharmacophore model for sulphonyl-urea (-cyanoguanidine) compounds with dual action, thromboxane receptor antagonists and thromboxane synthase inhibitors

A 3D pharmacophore model was developed for original sulphonyl-urea (-cyanoguanidine) compounds and known molecules which behave both as thromboxane receptor antagonists and as thromboxane synthase inhibitors. Five recognition sites appear to be essential for this dual activity: two hydrogen bond acceptors, an anionic site, a hydrophobic group and an aromatic ring. Such a model could be used to design new leads possessing the same pharmacological profile and to improve the activity of our compounds.

Nonsteroidal anti-inflammatory drugs in systemic lupus erythematosus

Up to 80% of patients with systemic lupus erythematosus (SLE) are treated with nonsteroidal anti-inflammatory drugs (NSAID) for musculoskeletal symptoms, serositis and headache. This survey reviews the literature on non-selective and selective inhibitors of cyclooxygenases, with an emphasis on the efficacy and safety profile reported in SLE patients. No lupus-specific data on gastro-intestinal side effects of NSAID exist. Both non-selective Cox inhibitors and selective Cox-2 inhibitors induce renal side effects, including sodium retention and reduction of the glomerular filtration rate. Lupus nephritis is a risk factor for NSAID-induced acute renal failure, but not for rare idiosyncratic toxic renal reactions to NSAID. In refractory nephrotic syndrome, NSAID have been used successfully. Cutaneous and allergic reactions to NSAID are increased in SLE patients as well as hepatotoxic effects, particularly with high dose aspirin. Whereas a variety of central nervous system side effects of NSAID are probably no more common in SLE patients than others, aseptic meningitis has been reported more frequently. Ovulation and pregnancy can be adversely affected by Cox inhibitors. The antiplatelet effect of aspirin and non-selective Cox inhibitors has a therapeutic potential in patients with antiphospholipid syndrome (APS). In summary, treatment of SLE with NSAID requires awareness for the increased frequency of some side effects and close monitoring of toxicity.

Thromboxane A(2) causes retarded clearance of aggregated protein in glomeruli of nephritic mice

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 serum albumin by mesangial cells in WT(+/+) mice, but not in the TP(-/-) mice. These findings suggest that thromboxane A(2) retards the clearance of aggregated protein in nephritic glomeruli and may contribute to the pathophysiology of glomerulonephritis.

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.

Renal haemodynamic characteristics in patients with lupus nephritis

OBJECTIVE

To clarify the characteristics of renal haemodynamics in patients with lupus nephritis (LN).

METHODS

The glomerular filtration rate (GFR) and renal plasma flow (RPF) of 37 patients with active LN were studied longitudinally over an interval of 8 to 144 weeks during treatment with corticosteroids or cytotoxic drugs, or both. All patients had clinical renal disorders and underwent renal biopsies.

RESULTS

Analysis of renal biopsy specimens showed that 31 patients had class IV LN. Class II, III, and VLN were present in two patients each. The average GFR increased significantly from 65.4 (SD 33.0) in the pretreatment stage to 86.6 (31.6) ml/min in the post-treatment stage, accompanied by an improvement in urinary or immunological abnormalities, or both. On the other hand, RPF decreased significantly from 625.2 (243.0) to 519.8 (179.0) ml/min. Therefore, the filtration fraction (FF) increased significantly from 10.7 (4.3)% to 16.8 (3.7)%. Low FF was recognised predominantly in patients with class IV LN, but was also observed in patients with other classes. The FF returned towards normal irrespective of the degree of GFR recovery. No significant changes were observed in the levels of blood pressure.

CONCLUSION

A reduction in GFR out of proportion to the reduction in RPF as demonstrated by the low FF values was related to the severity of LN or disease activity, or both. Therefore, relative evaluation of GFR and RPF, namely the determination of FF, may be a useful clinical parameter to determine the status of LN.