Toshiyuki Nagao

Effect of DP-1904, a thromboxane A2 synthase inhibitor, on passive Heymann nephritis in rats

The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane A2 synthase inhibitor, was evaluated using an experimental model of membranous nephropathy, viz. accelerated passive Heymann nephritis in which the glomerular injury is mediated by immune complexes. DP-1904 markedly inhibited the develop-ent of glomerular alteration as well as the elevation of proteinuria and plasma creatinine. When the treatment was started from the 22nd day, at which time proteinuria is fully developed, DP-1904 showed beneficial effects on proteinuria and glomerular histopathological changes. DP-1904 apparently decreased the deposition of both rabbit immunoglobulin G and rat immunoglobulin G on glomerular basement membrane in nephritic rats. A single administration of DP-1904 restored the decreased renal tissue blood flow, inhibited glomerular thromboxane B2 production and increased glomerular prostaglandin E2 and 6-keto prostaglandin F1 alpha production in nephritic rats. These results suggest that DP-1904 may be an effective agent for the treatment of idiopathic membranous nephropathy and that the beneficial effect of this drug may be due to the elimination of glomerular immune deposits and to an increase in renal tissue blood flow related to amelioration of the abnormal metabolism of arachidonic acid.

Effect of DP-1904, a thromboxane A2 synthetase inhibitor, on crescentic nephritis in rats

The antinephritic effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid hydrochloride], a thromboxane A2 synthetase inhibitor, was compared with that of OKY-046, using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Test drugs were given p.o. once daily from the day after the the development of glomerular alteration as well as the elevation of proteinuria and plasma cholesterol. On the other hand, OKY-046 (20 mg/kg per day), a thromboxane A2 synthetase inhibitor, significantly inhibited only deterioration in the glomeruli. DP-1904 and OKY-046 inhibited glomerular thromboxane B2 production and increased glomerular prostaglandin E2 and 6-keto prostaglandin F1 alpha production in normal and nephritic rats. Both drugs inhibited the increase in platelet aggregability, restored decreased renal tissue blood flow to a near-normal level and decreased the deposition of rat immunoglobulin G on glomerular basement membrane in nephritic rats. These results suggest that DP-1904 may be an effective agent for the treatment of proliferative glomerulonephritis.

Thromboxane A2 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.

Effect of lipo-prostaglandin E1 on crescentic-type anti-glomerular basement membrane nephritis in rats

The antinephritic effect of lipo-prostaglandin E1, prostaglandin E1 ((1R,2R,3R)-3-hydroxy-2-[(E)-(3S)-3-hydroxy-1-octenyl]-5-oxocyclopent ane heptanoic acid) incorporated in lipid microspheres was investigated using an experimental model of nephritis, crescentic-type anti-glomerular basement membrane nephritis. Lipo-prostaglandin E1 was given i.v. twice a day at 20, 40 and 80 microg/kg and azathioprine, an immunosuppressive agent, at 20 mg/kg was given p.o. once daily from the autologous phase, in which glomerulonephritis was fully developed (the 21 st day after injection of the anti-glomerular basement membrane serum), to the 50th day. Lipo-prostaglandin E1 (40 and 80 microg/kg x 2 per day) significantly inhibited the development of glomerular alterations as well as the elevation of proteinuria and plasma creatinine. Lipo-prostaglandin E1 (20 microg/kg x 2 per day) and azathioprine (20 mg/kg per day) significantly inhibited only the glomerular histopathological changes. Lipo-prostaglandin E1 at three doses significantly decreased the deposition of both rabbit immunoglobulin G and rat immunoglobulin G on the glomerular basement membrane in nephritic rats, but azathioprine apparently inhibited only the deposition of rat immunoglobulin G. A single administration of lipo-prostaglandin E1 inhibited the elevation of platelet aggregation and restored the decrease in renal tissue blood flow in nephritic rats. In addition, a single administration of lipo-prostaglandin E1 inhibited the elevation of glomerular thromboxane B2 and 6-keto prostaglandin F1alpha production in nephritic rats. These results suggest that lipo-prostaglandin E1 may be an effective agent for the treatment of glomerulonephritis. Its antinephritic effect may be due to the inhibition of platelet aggregation, an increase in renal tissue blood flow, a decrease in rabbit and rat immunoglobulin G deposition, and amelioration of the abnormal metabolism of arachidonic acid.

Adenosine 3', 5' cyclic monophosphate attenuates the production of fibronectin in the glomeruli of anti-glomerular basement membrane antibody-associated nephritic rats

Excessive production of extracellular matrix is thought to be involved in the progression of glomerulonephritis and glomerulosclerosis. In chronic glomerulonephritis, fibronectin has been shown to accumulate in the glomeruli, accompanied by cell proliferation. Glomerulonephritis was induced in rats by the injection of anti‐glomerular basement membrane antibody. The rats showed proteinuria and histological alterations in the glomeruli. An increase in fibronectin levels in the culture medium of isolated nephritic glomeruli was confirmed, and was associated with the development of nephritis. Immunohistochemical staining demonstrated a marked accumulation of fibronectin in the glomeruli of nephritic rats. Attenuated generation of cyclic AMP was also observed in the nephritic glomeruli treated with forskolin, prostaglandin E1 or adenosine. Forskolin, prostaglandin E2 and 8‐bromo‐cyclic AMP markedly reduced the production of fibronectin by the nephritic glomeruli compared with controls in a dose‐dependent manner. 8‐Bromo‐cyclic AMP suppressed the production of fibronectin by cultured mesangial cells. These findings suggest that the attenuated generation of cyclic AMP in response to ligands is connected to the augmented accumulation of fibronectin in nephritic glomeruli, and may facilitate the development of methods for treating glomerulonephritis and glomerulosclerosis.