Tomoji Kawabata

Antifibrotic action of pirfenidone and prednisolone : Different effects on pulmonary cytokines and growth factors in bleomycin-induced murine pulmonary fibrosis

Pirfenidone, a broad-spectrum antifibrotic agent, is known to have efficacy in certain fibrotic disease models, and is under clinical trials in patients with idiopathic pulmonary fibrosis. We investigated the antifibrotic effect of pirfenidone, and its regulatory effect on various pulmonary cytokines, in bleomycin-induced lung fibrosis in mice at the protein level, using prednisolone as a reference agent. Pirfenidone attenuated the bleomycin-induced pulmonary fibrosis at a minimum effective dose of 30 mg/kg/day t.i.d. from the analysis of lung hydroxyproline content. Both pirfenidone (30, 100 mg/kg/day t.i.d) and prednisolone (3, 15 mg/kg/day q.d.) suppressed lung inflammatory edema; however, prednisolone failed to suppress pulmonary fibrosis, which was significantly suppressed only by pirfenidone. Both pirfenidone and prednisolone suppressed the increase in lung interleukin (IL)-1beta, IL-6, IL-12p40 and monocyte chemoattractant protein (MCP)-1 levels induced by bleomycin. On the other hand, pirfenidone prevented the bleomycin-induced decrease in lung interferon (IFN)-gamma levels, while prednisolone had no such effect. Furthermore, pirfenidone suppressed elevation of lung basic-fibroblast growth factor (bFGF) and transforming growth factor (TGF)-beta1 levels, but prednisolone had no such effect. The increases in lung stroma cell derived factor (SDF)-1alpha and IL-18 were also suppressed. These findings suggest that pirfenidone exerts its antifibrotic effect through regulation of lung IFN-gamma, bFGF and TGF-beta1 levels during the development of bleomycin-induced pulmonary fibrosis in mice. The effect on SDF-1alpha and IL-18 levels may also be related to the antifibrotic effects of pirfenidone.

Biological characterization of human brain natriuretic peptide (BNP) and rat BNP: Species-specific actions of BNP

We examined the diuretic-natriuretic activities of rat BNP and human BNP in anesthetized rats in vivo and their vasorelaxant activities for rat thoracic aorta and porcine coronary artery in vitro. Rat BNP was almost equipotent to rat ANP in diuresis and natriuresis with relative potencies of 1.6 and 2.5, respectively, while human BNP exerted no significant activity. Rat ANP, rat BNP and human BNP relaxed PGF2 alpha-contracted rat aortic strips with IC50 values of 0.62, 0.64 and 12.1 nM, respectively, while they relaxed PGF2 alpha-contracted porcine coronary arteries with IC50 values of 0.04, 1.10 and 0.02 nM, respectively. These results strongly suggest that the biological action of BNP is species-specific.

ANTIPROTEINURIC EFFECT OF A THROMBOXANE RECEPTOR ANTAGONIST, S-1452, ON RAT DIABETIC NEPHROPATHY AND MURINE LUPUS NEPHRITIS

To shed light on the role of thromboxane A2 (TXA2) in renal injury, we evaluated the effects of S-1452, a TXA2 receptor antagonist, on rats with streptozotocin (STZ)-induced diabetic nephropathy and murine lupus nephritis. In STZ diabetes rats (n = 6), urinary protein excretion significantly increased from 8 weeks and was about 5 times as much as that in normal rats at 10 weeks after induction of diabetes. In S-1452-treated rats (n = 6), increase in urinary protein was rarely observed and was significantly inhibited at 8 and 10 weeks after induction of diabetes. In (NZB x NZW)F1 mice, no proteinuria was detected in vehicle controls (n = 20) and S-1452-treated mice (n = 20) from 0 to 8 weeks after initiation of S-1452 treatment. Proteinuria was observed in 3, 7 and 8 mice in the control group, and 0, 2 and 5 mice in the S-1452 group at 12, 16 and 20 weeks after initiation of S-1452 treatment, respectively. Proteinuria developed more slowly in S-1452-treated mice than in vehicle controls. In conclusion, TXA2 receptor antagonist, S-1452, suppresses the progression of renal injury.

The role of the C‐terminal region of rat brain natriuretic peptide in receptor selectivity

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) have different C‐terminal tail structures compared with the rather conservative ring structures which consist of 17 amino acid residues. To examine the different effects of the tail structures of ANP and BNP on their interaction with receptors, we synthesized several peptide analogs and measured their biological actions in three different assay systems. Deletion of the C‐terminal tail from rat BNP did not effect the vasorelaxation activity against rat aorta, but it promoted cGMP production in cultured rat aortic smooth muscle cells (RASMC). Deletion of the C‐terminal tail from rat ANP diminished both vasorelaxant and cGMP producing activities. In a binding competition assay with RASMC and [125I]rat ANP‐(1–28), the competition activities of both ANP and BNP were greatly reduced by C‐terminal deletion. In addition, we obtained agonists with novel receptor selectivity.