Pharmacologic properties of YM218, a novel, potent, nonpeptide vasopressin V1A receptor-selective antagonist

Early, but not late therapy with a vasopressin V1a-antagonist ameliorates the development of renal damage after 5/6 nephrectomy

Introduction. Vasopressin, mainly through the V1a-receptor, is thought to be a major player in the maintenance of hyperfiltration. Its inhibition could therefore lead to a decrease in progression of chronic renal failure.To this end, the effect of the vasopressin V1a-receptor-selective antagonist, YM218, was studied on proteinuria and focal glomerulosclerosis in early and late intervention after 5/6 nephrectomy in rats, and compared with an angiotensin-converting enzyme inhibitor (ACE-I).

Materials and methods. After 5/6 nephrectomy, early intervention was performed between week 2 and 10 thereafter with the V1a-receptor-selective antagonist (VRA, 10 mg/kg/day, n=10), enalapril (ACE-I, 10 mg/kg/day, n=9), or vehicle (n=8). Late intervention was performed in another group between week 6 and 12 with VRA (10 mg/kg/day, n=7), lisinopril (ACE-I, 5 mg/kg/day, n=7), or vehicle (n=7).

Results. In early intervention, proteinuria and focal glomerulosclerosis were significantly decreased by VRA compared to vehicle (44 7% and 59+8% respectively). ACE-I significantly decreased proteinuria (67 7%) and a trend towards a decrease in focal glomerulosclerosis was observed (30 18%). In late intervention, VRA did not decrease proteinuria and focal glomerulosclerosis compared to vehicle (21 20% and 0%, respectively),ACE-I significantly lowered proteinuria (92 2%) and a focal glomerulosclerosis (69+1%) lowering trend was observed.

Conclusion. These results indicate that VRA may protect against early progression of renal injury after 5/6 nephrectomy, whereas its effectiveness seems limited in established renal damage.

Oxytocin and vasopressin modulate the social response to threat: a preclinical study

Individuals in many species increase their proximity to others in threatening situations (defensive aggregation), increasing their chance of survival and reducing the adverse psychological impact of stressors. However, the basic neurobiology of defensive aggregation is not well understood. Here we examined the role of the social neuropeptides oxytocin (OT) and vasopressin (AVP) in this response. Groups of rats were exposed to a ball of cat fur (an innate threat stimulus) in a large arena, causing prolonged periods of tight social grouping (huddling). The modulatory effects of OT and AVP on huddling were examined both alone and in conjunction with relevant antagonists. To determine specificity of treatment effects to social grouping, the effects of the same treatments were also assessed in individual rats exposed to cat fur and given the opportunity to hide. OT (0.5 mg/kg, i.p.) and AVP (0.01 mg/kg, i.p.) increased huddling in rats socially exposed to cat fur, whereas the selective V1A AVP receptor antagonist SR49059 (3 mg/kg, i.p.) decreased huddling. The effects of OT were prevented by pre-treatment with SR49059 (3 mg/kg), while those of AVP were prevented by the V1B receptor antagonist SSR149415 (30 mg/kg, i.p.). OT had no effect on huddling when groups of four rats were tested with no cat fur present whereas AVP increased huddling under these conditions. Neither OT, nor SR49059, affected hiding in individual rats exposed to cat fur. However, AVP increased hiding, an effect prevented by SSR149415 (30 mg/kg, i.p.). These results suggest that OT acts on V1A receptors to promote a social response to threat without altering the more general defensive response. Conversely, AVP appears to increase generalised anxiety via V1B receptors, which subsequently results in huddling. A hitherto unrecognised function of oxytocin is therefore to promote social affiliation during threatening situations.

Downregulation of vasopressin V1A receptors and activation of mitogen-activated protein kinase in rat mesangial cells cultured under high-glucose conditions

SUMMARY

In the present study we examined the effects of high extracellular glucose concentrations on vasopressin (AVP) V(1A) receptor kinetics and signal transduction in cultured rat mesangial cells. Scatchard analysis of [(3) H]-AVP binding to mesangial cell plasma membranes showed that although high glucose (30 mmol/L) decreased V(1A) receptor numbers relative to cells cultured in normal glucose (10 mmol/L), receptor affinity was not affected. This V(1A) receptor downregulation was associated with an attenuated increase in AVP-stimulated cytosolic free calcium concentrations ([Ca(2+) ](i) ). In addition, high glucose increased both the basal and AVP-stimulated activity of the classic mitogen-activated protein kinase, namely extracellular signal-regulated kinase (ERK). Furthermore, high glucose induced activation of protein kinase C (PKC) in mesangial cells that could be inhibited by coincubation with the PKC inhibitor staurosporine (10 nmol/L). Staurosporine also markedly attenuated the high glucose-induced downregulation of V(1A) receptors on mesangial cells and blocked the depressed [Ca(2+) ](i) response and increased ERK activity induced by AVP. The results indicate that high extracellular glucose downregulates V(1A) receptors on rat mesangial cells and modulates their signal transduction properties via PKC activation.

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 V(1A) 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.

In vitro and in vivo pharmacological characterisation of the potent and selective vasopressin V(1A) receptor antagonist 4-[4-(4-Chloro-phenyl)-5-[1,2,3]triazol-2-ylmethyl-4H-[1,2,4]triazol-3-yl]-piperidin-1-yl-(3,5-difluoro-phenyl) methanone (PF-00738245)

The dysregulation of arginine vasopressin (AVP) release and activation of vasopressin receptors plays an important role in disease conditions including polycystic kidney disease, congestive heart failure and dysmenorrhoea. The development of potent and selective vasopressin receptor ligands is needed to help dissect the function of the specific subtypes in disease pathogenesis. Here we report the pharmacological characterisation of PF-00738245 in in vitro binding and functional assays using cells expressing vasopressin V(₁A), V(₁B) or V₂ receptors. PF-00738245 inhibited AVP binding to the recombinant human vasopressin V(₁A) receptor (K(i)=2.85 nM) and blocked AVP-induced rat aortic ring and human myometrial contraction (pK(B)=7.35 and 8.62 respectively). PF-00738245 was selective for the vasopressin V(1A) receptor by demonstrating minimal binding to vasopressin V(₁B) (3.6% inhibition at 10 μM) or functional activity at vasopressin V₂ receptors (8.1% agonist and -8.4% antagonist activity at 10 μM) as well as the oxytocin receptor (46.3% antagonist activity at 10 μM). The in vivo pharmacological properties were tested orally in the rat and PF-00738245 dose dependently blocked the effect of AVP on a capsaicin-induced cutaneous flare response. Taken together the data support the use of PF-00738245 as a potent and selective vasopressin V(₁A) receptor antagonist which may have utility in the treatment of disease conditions which are propagated by elevation in vasopressin V(₁A) receptor signalling.

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.

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 V(1A) receptor-selective antagonist, confirming this is a V(1A) 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 V(1A) receptor-selective antagonist and partially abolished by the anti-VEGF antibody. These results indicate that AVP increases VEGF secretion in rat mesangial cells via V(1A) 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.

Effect of YM218, a nonpeptide vasopressin V1A receptor-selective antagonist, on rat mesangial cell hyperplasia and hypertrophy

Mesangial cell growth constitutes a key feature of progressive glomerular injury. Vasopressin (AVP), a potent peptide vasoconstrictor, acts on mesangial cells through the V(1A) receptors, inducing contraction and cell proliferation. This study examined the effects of YM218, a nonpeptide AVP V(1A) receptor-selective antagonist, on the mitogenic and hypertrophic effects of AVP in rat mesangial cells. When added to mesangial cells whose growth was arrested, AVP concentration-dependently induced hyperplasia and hypertrophy. YM218 potently prevented AVP-induced hyperplasia and hypertrophy of these cells. Furthermore, AVP stimulated endothelin (ET)-1 secretion from mesangial cells in a concentration-dependent manner and this effect was potently inhibited by YM218. ET-1 also induced hyperplasia and hypertrophy in mesangial cells and this effect was completely abolished by ET(A) receptor-selective antagonist YM598. In addition, AVP-induced hyperplasia and hypertrophy were partly inhibited by YM598. These results suggest that AVP may modulate mesangial cell growth not only by its direct action but also through the stimulation of ET-1 secretion. YM218 displays high potency in inhibiting the AVP-induced physiologic responses of mesangial cells via the V(1A) receptors and is a potent pharmacologic probe for investigating the physiologic and pathophysiologic roles of AVP in several renal diseases.

Binding and signal transduction characteristics of the nonpeptide vasopressin V1A receptor-selective antagonist YM218 in cultured rat mesangial cells

Vasopressin (AVP) causes mesangial cell contraction, proliferation and hypertrophy. The present study investigated the effects of YM218, a potent, nonpeptide AVP V(1A) receptor-selective antagonist, on rat mesangial cells using binding, signal transduction and cell growth assays. Specific binding of (3)H-AVP to rat mesangial cell plasma 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 the expected V(1A) receptor profile. YM218 showed high affinity for V(1A) receptors, exhibiting a K(i) value of 0.19 nmol/l. AVP concentration-dependently increased intracellular Ca(2+) ([Ca(2+)](i)) levels, stimulated mitogen-activated protein (MAP) kinase and induced hyperplasia. Conversely, YM218 potently suppressed [Ca(2+)](i) elevation, activation of MAP kinase and hyperplasia induced by AVP. These results indicate that YM218 displays both high affinity for rat mesangial cell V(1A) receptors and high potency in inhibiting AVP-induced signal transduction and growth response. Therefore, YM218 is a useful pharmacologic tool for investigating the physiologic and pathophysiologic roles of AVP in kidney, and may have clinical application in the prevention or regression of mesangial cell growth.

Synthesis and biological activity of novel 4,4-difluorobenzazepine derivatives as non-peptide antagonists of the arginine vasopressin V1A receptor

To find potent and selective antagonists of the arginine vasopressin (AVP) V1A receptor, optimization studies of compounds structurally related to (Z)-N-{4'-[(4,4-difluoro-5-carbamoylmethylidene-2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl)carbonyl]phenyl}carboxamide were performed. The synthesis and pharmacological properties of these compounds are described. We first investigated the effect of the carboxamide moiety, and found that a 2-methylfuran-3-carbonyl group at this position increased V1A binding affinity and selectivity for the V1A receptor versus the V2 receptor. The amino group of the 5-carbamoylmethylidene moiety was also examined, and a 4-piperidinopiperidino group was found to be optimal at this position. The hemifumarate of compound 12l (YM218) was shown to exhibit potent binding affinity, V1A receptor selectivity, and in vivo antagonist activity.