Thioredoxin-interacting protein: a potential therapeutic target for treatment of progressive fibrosis in diabetic nephropathy.

Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of the antioxidant thioredoxin, and a critical agent in the in vivo regulation of glucose. The well-described induction of TXNIP by high glucose may represent an important pathogenic trigger of complications arising in the diabetic environment, with sustained overexpression of TXNIP triggering the increased production of reactive oxygen species and collagen, both major contributors to the development of diabetic nephropathy (DN). To examine a possible therapeutic role for targeted TXNIP inhibition in DN, transgenic (mRen-2)27 rats were rendered diabetic with streptozotocin and then treated with 20 μM TXNIP deoxyribozyme (DNAzyme) delivered continuously over 12 weeks by an implanted osmotic mini-pump.

Combination therapy of mesenchymal stem cells and serelaxin effectively attenuates renal fibrosis in obstructive nephropathy.

Chronic kidney disease (CKD) results from the development of fibrosis, ultimately leading to end-stage renal disease (ESRD). Although human bone marrow-derived mesenchymal stem cells (MSCs) can accelerate renal repair following acute injury, the establishment of fibrosis during CKD may affect their potential to influence regeneration capacity. Here we tested the novel combination of MSCs with the antifibrotic serelaxin to repair and protect the kidney 7 d post-unilateral ureteral obstruction (UUO), when fibrosis is established.

3',4'-Bis-difluoromethoxycinnamoylanthranilate (FT061): an orally-active antifibrotic agent that reduces albuminuria in a rat model of progressive diabetic nephropathy.

Cinnamoylanthranilates including tranilast have been identified as promising antifibrotics that can reduce fibrosis occurring in the kidney during diabetes, thereby delaying and/or preventing kidney dysfunction. Structure-activity relationships aimed at improving potency and metabolic stability have led to the discovery of FT061. This compound, which bears a bis-difluoromethoxy catechol, attenuates TGF-β-stimulated production of collagen in cultured renal mesangial cells (approx 50% at 3 μM).

A new anti-fibrotic drug attenuates cardiac remodeling and systolic dysfunction following experimental myocardial infarction.

Background: Pathological deposition of extracellular matrix in the non-infarct zone (NIZ) of the ventricle post myocardial infarction (MI) is a key contributor to cardiac remodeling and heart failure. FT011, a novel antifibrotic compound, was evaluated for its efficacy in neonatal cardiac fibroblasts (NCF) and in an experimental MI model.

Methods And Results: Collagen synthesis in NCF was determined by (3)H-proline incorporation following stimulation with TGF-β or angiotensin II (Ang II).

A purpose-synthesised anti-fibrotic agent attenuates experimental kidney diseases in the rat.

Background And Purpose: Locally-active growth factors have been implicated in the pathogenesis of many diseases in which organ fibrosis is a characteristic feature. In the setting of chronic kidney disease (CKD), two such pro-fibrotic factors, transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF) have emerged as lead potential targets for intervention. Given the incomplete organ protection afforded by blocking the actions of TGF-β or PDGF individually, we sought to determine whether an agent that inhibited the actions of both may have broader effects in ameliorating the key structural and functional abnormalities of CKD.

eNOS deficiency predisposes podocytes to injury in diabetes.

Endothelial nitric oxide synthase (eNOS) deficiency may contribute to the pathogenesis of diabetic nephropathy in both experimental models and humans, but the underlying mechanism is not fully understood. Here, we studied two common sequelae of endothelial dysfunction in diabetes: glomerular capillary growth and effects on neighboring podocytes. Streptozotocin-induced diabetes increased glomerular capillary volume in both C57BL/6 and eNOS(-/-) mice.

FT011, a new anti-fibrotic drug, attenuates fibrosis and chronic heart failure in experimental diabetic cardiomyopathy.

Aims: Cardiac remodelling in diabetes includes pathological accumulation of extracellular matrix and myocyte hypertrophy that contribute to heart dysfunction. Attenuation of remodelling represents a potential therapeutic target. We tested this hypothesis using a new anti-fibrotic drug, FT011 (Fibrotech Therapeutics Pty Ltd), on diabetic Ren-2 rats, a model which replicates many of the structural and functional manifestations of diabetic cardiomyopathy in humans.

Protein kinase C β inhibition ameliorates experimental mesangial proliferative glomerulonephritis.

Aim: Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy where therapy targeting the β isoform of this enzyme has been examined. However, PKC-β is also increased in various forms of human glomerulonephritis, including IgA nephropathy. Accordingly, we sought to examine the effects of PKC-β inhibition in the Thy1.

Inhibition of the epidermal growth factor receptor preserves podocytes and attenuates albuminuria in experimental diabetic nephropathy.

Aim: Early renal enlargement may predict the future development of nephropathy in patients with diabetes. The epidermal growth factor (EGF)-EGF receptor (EGFR) system plays a pivotal role in mediating renal hypertrophy, where it may act to regulate cell growth and proliferation and also to mediate the actions of angiotensin II through transactivation of the EGFR. In the present study we sought to investigate the effects of long-term inhibition of the EGFR tyrosine kinase in an experimental model of diabetes that is characterized by angiotensin II dependent hypertension.

Tranilast attenuates the up-regulation of thioredoxin-interacting protein and oxidative stress in an experimental model of diabetic nephropathy.

Background: Diabetic nephropathy is the leading cause of kidney failure in the developed world. Tranilast has been reported to not only act as an anti-inflammatory and anti-fibrotic compound, but it also exerts anti-oxidative stress effects in diabetic nephropathy. Thioredoxin-interacting protein (Txnip) is the endogenous inhibitor of the anti-oxidant thioredoxin and is highly up-regulated in diabetic nephropathy, leading to oxidative stress and fibrosis.

Evaluation and optimization of antifibrotic activity of cinnamoyl anthranilates.

Tranilast is an anti-inflammatory drug in use for asthma and atopic dermatitis. In studies over the last decade it has been revealed that tranilast can reduce fibrosis occurring in the kidney during diabetes, thereby delaying and/or preventing kidney dysfunction. We report a structure-activity study aimed at optimizing the antifibrotic activity of tranilast.

Inhibition of protein kinase C-beta by ruboxistaurin preserves cardiac function and reduces extracellular matrix production in diabetic cardiomyopathy.

Background: Heart failure is a common cause of morbidity and mortality in diabetic patients that frequently manifests in the absence of impaired left ventricular systolic function. In contrast to the strong evidence base for the treatment of systolic heart failure, the treatment of heart failure with preserved left ventricular function is uncertain, and therapeutic targets beyond blockade of the renin-angiotensin-aldosterone and beta-adrenergic systems are being sought. One such target is the beta-isoform of protein kinase C (PKC), implicated in both the complications of diabetes and in cardiac dysfunction in the nondiabetic setting.

The (Pro)renin receptor: site-specific and functional linkage to the vacuolar H+-ATPase in the kidney.

The (pro)renin receptor ([P]RR) is a transmembrane protein that binds both renin and prorenin with high affinity, increasing the catalytic cleavage of angiotensinogen and signaling intracellularly through mitogen-activated protein kinase activation. Although initially reported as having no homology with any known membrane protein, other studies have suggested that the (P)RR is an accessory protein, named ATP6ap2, that associates with the vacuolar H(+)-ATPase, a key mediator of final urinary acidification. Using in situ hybridization, immunohistochemistry, and electron microscopy, together with serial sections stained with nephron segment-specific markers, we found that (P)RR mRNA and protein were predominantly expressed in collecting ducts and in the distal nephron.

Expression, localization, and function of the thioredoxin system in diabetic nephropathy.

Excessive reactive oxygen species play a key role in the pathogenesis of diabetic nephropathy, but to what extent these result from increased generation, impaired antioxidant systems, or both is incompletely understood. Here, we report the expression, localization, and activity of the antioxidant thioredoxin and its endogenous inhibitor thioredoxin interacting protein (TxnIP) in vivo and in vitro. In normal human and rat kidneys, expression of TxnIP mRNA and protein was most abundant in the glomeruli and distal nephron (distal convoluted tubule and collecting ducts).

Protein kinase C-beta inhibition attenuates the progression of nephropathy in non-diabetic kidney disease.

Background: Activation of protein kinase C (PKC) has been implicated in the pathogenesis of diabetic nephropathy where therapy targeting the beta isoform of this enzyme is in advanced clinical development. However, PKC-beta is also increased in various forms of human glomerulonephritis with several potentially nephrotoxic factors, other than high glucose, resulting in PKC-beta activation. Accordingly, we sought to examine the effects of PKC-beta inhibition in a non-diabetic model of progressive kidney disease.

Role of VEGF in maintaining renal structure and function under normotensive and hypertensive conditions.

Inhibiting the actions of VEGF is a new therapeutic paradigm in cancer management with antiangiogenic therapy also under intensive investigation in a range of nonmalignant diseases characterized by pathological angiogenesis. However, the effects of VEGF inhibition on organs that constitutively express it in adulthood, such as the kidney, are mostly unknown. Accordingly, we examined the effect of VEGF inhibition on renal structure and function under physiological conditions and in the setting of the common renal stressors: hypertension and activation of the renin-angiotensin system.

Tranilast attenuates diastolic dysfunction and structural injury in experimental diabetic cardiomyopathy.

Diastolic dysfunction is an increasingly recognized complication of diabetes that develops in relatively young patients as a result of diabetic cardiomyopathy (DCM). With recent advances in echocardiographic technology now permitting the reliable assessment of diastolic function in the rat, we examined cardiac function and structure in diabetic rodents and assessed the effects of intervening with tranilast, an antifibrotic compound that has been shown to attenuate the actions of transforming growth factor-beta (TGF-beta) in cardiac fibroblasts. We also sought to examine the mechanism whereby tranilast inhibits the actions of TGF-beta.

Effects on protein kinase C-beta inhibition on glomerular vascular endothelial growth factor expression and endothelial cells in advanced experimental diabetic nephropathy.

Ruboxistaurin is an inhibitor of the beta isoform of protein kinase C (PKC-beta) that reduces the actions of vascular endothelial growth factor (VEGF) and attenuates the progression of diabetic retinopathy. In the glomerulus VEGF is constitutively expressed where it likely has a role in maintaining endothelial cell integrity, particularly in disease states. Given its potential use in diabetic nephropathy, we sought to determine the effects of PKC-beta inhibition on VEGF and glomerular endothelial cells in experimental diabetic nephropathy.

Renal expression and localization of the facilitative glucose transporters GLUT1 and GLUT12 in animal models of hypertension and diabetic nephropathy.

Renal tubular glucose reabsorption is mediated by facilitative glucose transporter (GLUT) proteins and energy-dependent sodium glucose luminal transporters. Glucose transport in the diabetic kidney is upregulated and has been implicated in the pathogenesis of progressive diabetic nephropathy. Hyperglycemia, hypertension, and activation of the renin-angiotensin system are believed important in the development of the disease.

Inhibition of protein kinase C reduces left ventricular fibrosis and dysfunction following myocardial infarction.

Despite current therapies, chronic heart failure (CHF) remains a major complication of myocardial infarction (MI). The pathological changes that follow MI extend to regions remote from the site of infarction (non-infarct zone, NIZ) where fibrosis is a prominent finding. Although the mechanisms underlying this adverse remodeling are incompletely understood, activation of protein kinase C has recently been implicated in its pathogenesis.

Tranilast attenuates cardiac matrix deposition in experimental diabetes: role of transforming growth factor-beta.

Objective: The pathological accumulation of extracellular matrix is a characteristic feature of diabetic cardiomyopathy that is directly related to a loss of function. Tranilast (n-[3,4-anthranilic acid), used for the treatment of fibrotic skin diseases, has also been shown to inhibit transforming growth factor-beta (TGF-beta)-induced matrix production in kidney epithelial cells.

Methods: To investigate the effects of tranilast in the diabetic heart, we examined its effects in cultured cardiac fibroblasts and then assessed its effects in (mRen-2)27 diabetic rats with established disease (8 weeks after streptozotocin).

Platelet-derived growth factor receptor transactivation mediates the trophic effects of angiotensin II in vivo.

In addition to the modulation of vascular tone, angiotensin II (Ang II) has growth factor-like effects in vascular tissue. The mechanisms whereby Ang II mediates these trophic actions are incompletely understood but are thought to include effects on systemic blood pressure, stimulation of transforming growth factor-beta (TGF-beta) expression, and transactivation of growth factor receptor kinases. To investigate the role of platelet-derived growth factor receptor (PDGFR) transactivation in mediating the growth factor-like effects of Ang II we administered Ang II (200 ng/kg per minute) or saline to male Sprague-Dawley rats by osmotic minipump for 12 days and treated with imatinib mesylate, an inhibitor of the PDGFR tyrosine kinase.

A study of VEGF and its receptors in two rat models of proteinuria.

Background: The high level of expression of vascular endothelial growth factor (VEGF) in normal podocyte foot processes suggests that VEGF has an important role in maintaining normal glomerular function. While altered VEGF expression occurs in many glomerular diseases, a direct role for VEGF in the pathogenesis of proteinuria has not been demonstrated.

Methods: Expression of VEGF and its receptors (VEGFR-1 and VEGFR-2) was examined in passive Heymann nephritis (PHN) and puromycin aminonucleoside nephrosis (PAN), by immunohistochemistry, in situ hybridization, Northern and Western blotting.

Does vascular endothelial growth factor (VEGF) play a role in the pathogenesis of minimal change disease?

Background: Minimal change disease (MCD) is one of the major causes of nephrotic syndrome both in children and adults. The pathogenesis of this condition is not clear and it has been suggested that a plasma permeability factor may play a role. Vascular endothelial growth factor (VEGF), also known as vascular permeability factor, has been thought to be one the factors involved.