Takeyuki Yatsu

Vasopressin increases type IV collagen production through the induction of transforming growth factor-beta secretion in rat mesangial cells

Production of extracellular matrix proteins, such as type IV collagen, by mesangial cells contributes to progressive glomerulosclerosis. Transforming growth factor-beta (TGF-beta) modulates mesangial cell growth and stimulates extracellular matrix synthesis by mesangial cells. In this study, the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate type IV collagen production and correlation with TGF-beta secretion by cultured rat mesangial cells was examined. AVP induced a time- and concentration-dependent increase in TGF-beta secretion and mitogenic effect in rat mesangial cells. This AVP-induced increase in TGF-beta secretion was potently inhibited by AVP V(1A) receptor-selective antagonist. AVP also induced a concentration-dependent increase in the production of type IV collagen and this effect was inhibited by V(1A) receptor-selective antagonist. Furthermore, TGF-beta also induced an increase in the production of type IV collagen; the AVP-enhanced production of type IV collagen was inhibited by an anti-TGF-beta antibody. These results demonstrate that AVP stimulates synthesis of type IV collagen by cultured rat mesangial cells through the induction of TGF-beta synthesis mediated by V(1A) receptors. Therefore, AVP-induced TGF-beta secretion by proliferating mesangial cells might act as an autocrine factor to regulate synthesis of extracellular matrix; this mechanism may contribute to glomerulosclerosis in renal diseases including diabetic nephropathy.

VASOPRESSIN STIMULATES THE PRODUCTION OF EXTRACELLULAR MATRIX BY CULTURED RAT MESANGIAL CELLS

1 Mesangial expansion, an indicator of chronic glomerular diseases, occurs as a result of the excessive accumulation of extracellular matrix (ECM) proteins, such as type IV collagen. In order to investigate the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to induce ECM production, an enzyme‐linked immunosorbent assay was used to measure type I and IV collagen and fibronectin produced from cultured rat mesangial cells. 2 Addition of AVP (0.01–1000 nmol/L) caused a significant and concentration‐dependent production of secreted and cell‐associated ECM, type I collagen, type IV collagen and fibronectin by cultured rat mesangial cells. The AVP V1A receptor‐selective antagonist YM218 (0.01–1000 nmol/L) potently and concentration‐dependently inhibited the induced increase in ECM production caused by AVP, but the V2 receptor‐selective antagonist SR 121463A (0.1–1000 nmol/L) did not potently inhibit. 3 Vasopressin inhibited the synthesis of matrix metalloproteinase (MMP)‐2, which degrades matrix proteins, including type IV collagen, and stimulated endothelin (ET)‐1 secretion from mesangial cells. These effects were potently inhibited by YM218, but not by SR 121463A. 4 In addition, 10 nmol/L ET‐1 inhibited the synthesis of MMP‐2 and stimulated ECM production in mesangial cells. These effects were completely abolished by the ETA receptor‐selective antagonist YM598 (1 mmol/L); however, the ETB receptor‐selective antagonist BQ‐788 (1 mmol/L) and the AVP receptor antagonists YM218 and SR 121463A did not inhibit ET‐1‐induced inhibition of MMP‐2 synthesis and ECM production. In addition, AVP‐induced inhibition of MMP‐2 synthesis and ECM production were partly inhibited by YM598. 5 These findings indicate that AVP may modulate ECM production not only via a direct action on V1A receptors, but also through stimulation of ET‐1 secretion. Vasopressin may contribute to the glomerular remodelling and ECM accumulation observed in glomerular diseases.

Dopamine DA1 receptor agonist activity of YM435 in the canine renal vasculature

1. The renal vasodilatory effect of YM435 was used as an index of its dopamine DA1 receptor agonist activity and compared with that of dopamine in pentobarbital-anesthetized dogs. 2. Intrarenal arterial administration of YM435 (0.1 to 10 micrograms) and dopamine (1 to 100 micrograms) produced a dose-dependent increase in renal blood flow. The doses of YM435 and dopamine required to cause a 30-ml/min increase in renal blood flow were 2.0 and 26.8 micrograms intra-arterially (IA), respectively. YM435 was therefore 13 times more potent than dopamine in this effect. 3. The selective dopamine DA1 receptor antagonist, SCH 23390, but not the selective dopamine DA2 receptor antagonist, nemonapride, caused dose-dependent, parallel shifts to the right in the dose-responsive curve of YM435. 4. The present results demonstrate that YM435 is a potent and selective dopamine DA1 receptor agonist.

Vasopressin induces human mesangial cell growth via induction of vascular endothelial growth factor secretion

Vasoactive hormones, growth factors, and cytokines are important in promoting mesangial cell growth, a characteristic feature of many glomerular diseases. Vascular endothelial growth factor (VEGF) is an endothelial mitogen and promoter of vascular permeability that is constitutively expressed in human glomeruli, but its role in the kidney is still unclear. In the present study, we investigated the ability of vasopressin (AVP) to stimulate VEGF secretion by and correlation with AVP-induced cell growth in human mesangial cells. AVP caused time- and concentration-dependent increases in VEGF secretion from human mesangial cells, which was in turn potently inhibited by a V(1A) receptor-selective antagonist, confirming that this secretion is a V(1A) receptor-mediated event. VEGF also induced mesangial cell growth which was completely inhibited on administration of an anti-VEGF neutralizing antibody. Further, AVP-induced mesangial cell growth was completely abolished by the V(1A) receptor-selective antagonist and partially inhibited by an anti-VEGF neutralizing antibody. These results suggest that AVP stimulates VEGF secretion by human mesangial cells via V(1A) receptors. This secreted VEGF may function as an autocrine hormone to regulate mesangial cell growth, a mechanism by which AVP might contribute to progressive glomerular diseases such as diabetic nephropathy.

Synthesis and structure-activity relationships of amide derivatives of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetic acid as selective arginine vasopressin V2 receptor agonists.

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives was synthesized, and their structure-activity relationships were examined in order to identify potent and selective arginine vasopressin V(2) receptor agonists. Attempts to substitute other chemical groups in place of the 2-pyridilmethyl moiety of 1a led to the discovery that potent V(2) binding affinity could be obtained with a wide range of functional groups. This structural tolerance allowed for the manipulation of other attributes, such as selectivity against V(1a) receptor affinity or avoidance of the undesirable inhibition of cytochrome P450 (CYP), without losing potent affinity for the V(2) receptor. Some representative compounds obtained in this study were also found to decrease urine volume in awake rats.

Characterization of vasopressin receptor in rat lung

This study characterized rat lung membrane arginine vasopressin (AVP) receptors in detail. Specific binding of [3H]AVP to rat lung membranes was dependent upon time, temperature and membrane protein concentration. Scatchard plot analysis of equilibrium binding data revealed the existence of a single class of high-affinity binding sites with a Kd of 0.45 nM and a Bmax of 76.6 fmol/mg protein. Competitive inhibition of [3H]AVP binding showed that neurohypophysial hormones as well as their synthetic analogues displaced [3H]AVP in a concentration-dependent manner. The order of potencies for the native peptides was: AVP > lysine vasopressin = arginine vasotocin > oxytocin. Furthermore, potent V1A receptor antagonists, d(CH2)5Tyr(Me)AVP and dPTyr(Me)AVP, showed high affinity for lung membranes. In contrast, the V2 receptor agonist, dDAVP, and the specific oxytocin receptor agonist, [Thr4,Gly7]oxytocin, did not affect AVP binding. These results suggest that the lung contains the V1A receptor subtype. The lung membrane AVP receptor characterized in this study may play an important role in mediating the physiological effects of AVP in the lung.

Preparation of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepin-5-ylidene)acetamide derivatives as novel arginine vasopressin V2 receptor agonists

The present work describes the discovery of novel series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin (AVP) V(2) receptor agonists. By replacing the amide juncture in YM-35278 with a direct ring connection gave compound 10a, which acts as a V(2) receptor agonist. These studies provided the potent, orally active non-peptidic V(2) receptor agonists 10a and 10j.

Effects of high glucose on AVP-induced hyperplasia, hypertrophy, and type IV collagen synthesis in cultured rat mesangial cells.

Introduction. Hyperglycemia is a principal characteristic of diabetes and influences many cellular functions. Diabetic nephropathy is characterized by glomerular mesangial expansion which could result from increased mesangial cell extracellular matrix synthesis induced by hyperglycemia. Methods. To investigate whether the physiological functions of mesangial cells are altered in a diabetic environment, we evaluated the effect of high extracellular glucose concentration on thymidine/leucine incorporation, hyperplasia/hypertrophy, and type IV collagen synthesis, induced by vasopressin (AVP), in cultured rat mesangial cells. Results. The exposure of mesangial cells to a high glucose concentration (30 mM) significantly reduced AVP-induced thymidine incorporation and hyperplasia compared with normal glucose (10 mM). By contrast, treatment of mesangial cells with AVP in the presence of high extracellular glucose significantly increased leucine incorporation, hypertrophy, and type IV collagen synthesis compared with those at normal glucose levels. The administration of staurosporine, a protein kinase C inhibitor, reversed these effects of high-glucose conditions. Furthermore, the nonpeptide AVP V1A receptor-selective antagonists potently inhibited these AVP-induced physiological responses in mesangial cells cultured in high-glucose conditions. Conclusions. These results demonstrate that high glucose suppresses mesangial cell proliferation but enhances hypertrophy and type IV collagen synthesis induced by AVP. This increased mesangial cell hypertrophy and extracellular matrix synthesis may play a crucial role in the glomerular mesangial expansion common to diabetic nephropathy.

Effect of vasopressin on type IV collagen production in human mesangial cells

Production of extracellular matrix proteins, such as type IV collagen and fibronectin, by mesangial cells contributes to progressive glomerulosclerosis. In this study, the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate type IV collagen production by cultured human mesangial cells was examined using an enzyme-linked immunosorbent assay. AVP induced a concentration-dependent increase in the production of type IV collagen and this effect was potently and concentration-dependently inhibited by AVP V1A receptor antagonists, including YM218. AVP also induced a concentration-dependent increase in transforming growth factor (TGF)-beta secretion by human mesangial cells and this effect was inhibited by V1A receptor antagonists. Furthermore, TGF-beta also induced an increase in the production of type IV collagen; the AVP-enhanced production of type IV collagen was inhibited by an anti-TGF-beta antibody. These findings indicate that AVP stimulates synthesis of type IV collagen by cultured human mesangial cells through the induction of TGF-beta synthesis mediated by V1A receptors; consequently, AVP contributes to glomerular remodeling and extracellular matrix accumulation observed in glomerular diseases.

Vasopressin regulates rat mesangial cell growth by inducing autocrine secretion of vascular endothelial growth factor

Mesangial cell growth is a key feature of several glomerular diseases. Vascular endothelial growth factor (VEGF) is a potent mitogen of vascular endothelial cells and promoter of vascular permeability. Here, we examined the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate VEGF secretion from cultured rat mesangial cells. AVP potently induced a time- and concentration-dependent increase in VEGF secretion in these cells, which was then inhibited by a V1A receptor-selective antagonist, confirming this is a V1A receptor-mediated event. VEGF also induced hyperplasia and hypertrophy in mesangial cells, which was completely abolished by an anti-VEGF antibody. In addition, AVP-induced hyperplasia and hypertrophy were completely inhibited by the V1A receptor-selective antagonist and partially abolished by the anti-VEGF antibody. These results indicate that AVP increases VEGF secretion in rat mesangial cells via V1A receptors and modulates mesangial cell growth not only by direct action but also through stimulation of VEGF secretion. This autocrine mechanism might contribute to glomerulosclerosis in renal diseases such as diabetic nephropathy.