Involvement of protein kinase C in reduction of aggregated protein and phosphorylation of CREB in glomeruli.

We previously demonstrated the cAMP-PKA pathway to be associated with the reduction in aggregated proteins such as immune complex in glomeruli. The aim of this study was to clarify whether PKC is involved in the reduction of aggregated protein and phosphorylation of CREB in aggregated protein-loaded glomeruli. Mice were injected with aggregated bovine serum albumin (a-BSA), and glomeruli were isolated. The a-BSA-injected mice produced more cyclic AMP and had more phosphorylated serine and phosphorylated CREB in their glomeruli than the controls. The expression of phospho-CREB increased with the accumulation of a-BSA. KT5720 and H7 suppressed the increase in phosphorylated CREB in a-BSA-loaded glomeruli and the decrease in accumulated a-BSA in the glomeruli. These findings suggest that PKC is associated with the reduction of aggregated protein and phosphorylation of CREB in aggregated protein-loaded glomeruli.

Protective effect of prostaglandin EP4-receptor agonist on anti-glomerular basement membrane antibody-associated nephritis.

Prostaglandin E(2)-receptor subtypes, EP(1), EP(2), EP(3), and EP(4), are present in the kidney. The aim of this study was to elucidate the anti-nephritic effect of an EP(4)-receptor agonist on an experimental nephritic model. Mice were injected i.v. with anti-glomerulus antiserum to induce nephritis. Nephritic glomeruli generated more prostaglandin E(2) (2.6 and 0.7 ng) and less cyclic AMP than normal glomeruli (11 and 26 pmol). The production of cyclic AMP in nephritic glomeruli increased 67% in response to AE1-329, an EP(4) agonist, at 10(-5) M. Nephritic glomeruli expressed a lesser amount of mRNA of prostaglandin E(2)-receptor subtypes as compared with normal glomeruli. AE1-329 was administered s.c. at 100 microg/kg per day for 3 weeks. AE1-329 suppressed the increase in creatinine and cholesterol compared to those in the control nephritic mice. AE1-329-treated nephritic mice had less crescentic glomeruli and less deposition of rabbit IgG (anti-glomerular basement membrane antibody) in glomeruli than the control mice. AE1-329 prevented the development of glomerulonephritis. These findings suggest that EP(4)-receptor agonists are a promising drug to prevent the development of glomerulonephritis.

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

1. 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. 2. 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. 3. Attenuated generation of cyclic AMP was also observed in the nephritic glomeruli treated with forskolin, prostaglandin E1 or adenosine. 4. 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. 5. 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.

Effects of KD3-671, an angiotensin II type 1 receptor antagonist, on anti-thy-1 nephritis in rats.

We examined the effects of KD3-671 (2-propyl-8-oxo-1-[(2'-(H-tetrazole-5-yl)biphenyl-4-yl)methyl]-4,5,6,7-tetrahydrocycloheptimidazole), an angiotensin II type1 receptor antagonist, on an experimental rat model of mesangioproliferative glomerulonephritis, anti-Thy-1 nephritis. Anti-Thy-1 nephritis was induced by intravenous injection of 300 microg/kg of anti-Thy-1.1 monoclonal antibody into rats. KD3-671 (3, 10, 30 mg/kg per day) or enalapril (30 mg/kg per day), an angiotensin II converting enzyme inhibitor, was given p.o. once daily from the day before the antibody injection (the 1st day) to the 15th day after. KD3-671 significantly inhibited an increase in the number of total and proliferating cell nuclear antigen-positive cells and the deposition of alpha-smooth muscle actin and fibronectin in the glomeruli of nephritic rats, but enalapril (30 mg/kg per day) suppressed only the number of total cells and the deposition of alpha-smooth muscle actin in the glomeruli. Moreover, to elucidate the effect of KD3-671 on matrix deposition in the glomeruli, we measured the production of fibronectin in isolated glomeruli obtained from anti-Thy-1 nephritic rats. The glomeruli in anti-Thy-1 nephritic rats produced more fibronectin than that in control rats. KD3-671 (10(-8), 10(-7), 10(-6) M) dose-dependently attenuated fibronectin production in isolated nephritic glomeruli. These findings suggest that KD3-671 may be an effective agent for the treatment of mesangioproliferative glomerulonephritis.

Antiproteinuric effect of KD3-671, an angiotensin II type 1 receptor antagonist, in rats with accelerated passive Heymann nephritis.

The antiproteinuric effect of KD3-671 (2-propyl-8-oxo-1-[(2'-(H-tetrazole-5-yl)biphenyl-4-yl)methyl]-4,5,6,7-tetrahydrocycloheptimidazole), an angiotensin II type 1 receptor antagonist, was compared with that of enalapril, an angiotensin 11-converting enzyme inhibitor, using an experimental model of membranous nephropathy. KD3-671 (3, 10 and 30 mg/kg per day) and enalapril (30 mg/kg per day) were given p.o. for 40 days, respectively. KD3-671 (30 mg/kg per day) inhibited the elevation of proteinuria and plasma total cholesterol. On the other hand, enalapril showed only a tendency to diminish these parameters. KD3-671 had an antiproteinuric effect in rats with accelerated passive Heymann nephritis. These findings provide considerable encouragement for the clinical development of KD3-671.