Tranilast inhibits transplant-associated coronary arteriosclerosis in a murine model of cardiac transplantation

Tranilast: a review of its therapeutic applications

Tranilast (N-[3',4'-dimethoxycinnamoyl]-anthranilic acid) is an analog of a tryptophan metabolite. Initially, tranilast was identified as an anti-allergic agent, and used in the treatment of inflammatory diseases, such as bronchial asthma, atypical dermatitis, allergic conjunctivitis, keloids and hypertrophic scars. Subsequently, the results showed that it could be also effective in the management of a wide range of conditions. The beneficial effects of tranilast have also been seen in a variety of disease states, such as fibrosis, proliferative disorders, cancer, cardiovascular problems, autoimmune disorders, ocular diseases, diabetes and renal diseases. Moreover, several trials have shown that it has very low adverse effects and it is generally well tolerated by patients. In this review, we have attempted to accurately summarize previously published studies relating to the use of tranilast for a range of disorders and discuss the drug's possible mode of action. The major mode of the drug's efficacy appears to be the suppression of the expression and/or action of the TGF-β pathway, but the drug affects other factors as well. The findings presented in this review demonstrate the potential of tranilast for the control of a vast array of pathological situations, furthermore, it is a prescribed drug without severe side effects.

Tranilast alleviates endothelial dysfunctions and insulin resistance via preserving glutathione peroxidase 1 in rats fed a high-fat emulsion

We investigated the effects of treatment with tranilast on vascular and metabolic dysfunction induced by a high-fat emulsion intragastric administration. Wistar rats were randomized to receive water or high-fat emulsion with or without tranilast treatment (400 mg/kg per day) for 4 weeks. Insulin sensitivity was determined with a hyperinsulinemic-euglycemic clamp experiment and short insulin tolerance test. Vascular reactivity was evaluated using aortic rings in organ chambers. Glutathione peroxidase 1 (GPX1) expressions, eNOS phosphorylation and activity, MCP-1, H2O2 formation, and NO production were determined in vascular or soleus tissues. Tranilast treatment was found to prevent alterations in vascular reactivity and insulin sensitivity and to prevent increases in plasma glucose and insulin noted in the high-fat emulsion-treated rats. These were associated with increased antioxidant enzyme GPX1 expression, eNOS phosphorylation and activity, and NO production, but reductions in H2O2 accumulation. Moreover, tranilast preserved GPX1 expression in palmitic acid (PA)-treated endothelial cells with a consequent decreased ROS formation and increased eNOS phosphorylation and NO production. Therefore, oxidative stress induced by a relatively short-term high-fat diet could cause the early development of vascular and metabolic abnormalities in rats, and tranilast has a beneficial effect in vascular dysfunctions and insulin resistance via preserving GPX1 and alleviating oxidative stress.

Early and delayed tranilast treatment reduces pathological fibrosis following myocardial infarction

BACKGROUND

Tranilast has been shown to inhibit TGFβ1-related fibrosis and organ failure in various disease models. We sought to examine the effects of tranilast on left ventricular (LV) remodelling post-MI.

METHODS

Following coronary artery ligation, Sprague Dawley rats were randomised to receive tranilast (300mg/kg/d, p.o.) or vehicle control over one of two treatment periods: (1) from 24h until seven days post-MI, (2) from seven days to 28 days post-MI. Cardiac tissue was harvested for molecular, immunohistochemical and cell culture analyses.

RESULTS

Tranilast treatment of MI rats from 24h until seven days post-MI reduced myocardial collagen content, α1 (I) procollagen, TGFβ1 and CTGF mRNA transcripts, monocyte/macrophage infiltration and exacerbated infarct expansion compared with vehicle-treatment. Delaying the commencement of tranilast treatment to seven days post-MI attenuated myocardial fibrosis, gene expression of α1(I) procollagen, α1(III) procollagen, fibronectin, TGFβ1 and CTGF mRNA transcripts, and monocyte/macrophage infiltration at 28d compared to vehicle-treatment, without detriment to infarct healing. Extended post-MI also preserved LV infarct size. In cultures of rat cardiac fibroblasts, tranilast attenuated TGFβ1-stimulated fibrogenesis.

CONCLUSION

Tranilast inhibits myocardial TGFβ1 expression, fibrosis in rat post-MI and collagen production in cardiac fibroblasts. While tranilast intervention from 24h post-MI exacerbated infarct expansion, delaying the commencement of treatment to seven days post-MI impeded LV remodelling.

Pathophysiology of abdominal aortic aneurysm relevant to improvements in patients' management

PURPOSE OF REVIEW

Abdominal aortic aneurysm (AAA) is being diagnosed more frequently in older patients due to the increased use of abdominal imaging and the rising average age of western populations. Currently the management of this condition has two important deficiencies: inadequate methods to identify AAAs at risk of progression and rupture and the current lack of effective nonsurgical therapies. In this review recent developments in identifying new diagnostic, prognostic and therapeutic strategies for AAA are discussed.

RECENT FINDINGS

There are growing number of animal and human association studies which have identified markers and strategies of potential value in improving identification, monitoring and treatment of AAA.

SUMMARY

Selective large prospective imaging, biomarker and intervention studies are now required to clearly demonstrate the value of new management pathways for AAA.

Control of cell proliferation in atherosclerosis: insights from animal models and human studies

Excessive hyperplastic cell growth within occlusive vascular lesions has been recognized as a key component of the inflammatory response associated with atherosclerosis, restenosis post-angioplasty, and graft atherosclerosis after coronary artery bypass. Understanding the molecular mechanisms that regulate arterial cell proliferation is therefore essential for the development of new tools for the treatment of these diseases. Mammalian cell proliferation is controlled by a large number of proteins that modulate the mitotic cell cycle, including cyclin-dependent kinases, cyclins, and tumour suppressors. The purpose of this review is to summarize current knowledge about the role of these cell cycle regulators in the development of native and graft atherosclerosis that has arisen from animal studies, histological examination of specimens from human patients, and genetic studies.

The experimental study of cardiac allograft vasculopathy and myocardial fibrosis in rats

We sought to analyze the development of myocardial fibrosis and cardiac allograft vasculopathy (CAV) as a theoretical basis for the prevention and treatment of rejection. Heterotopic cardiac transplantation was performed from Wistar rats to Sprague-Dawley rats. The recipients pretreated with donor splenocyte (SPC) infusion followed by cyclophosphamide (CP) were divided into 3 groups: Control animals without immunosuppression (Group 1; n = 10); Group 2, CsA treatment (n = 10) with euthanasia 2-3 months posttransplantation; and Group 3 (n = 20), CP plus SPC treatment with 10 recipients euthanized at 2 weeks posttransplantation and 10 animals monitored for at least 1 year posttransplantation. Histological studies were performed to evaluate myocardial fibrosis and CAV; 2-3 days after transplantation, there was abundant infiltration of collagenous fibers in the adventitia and intima of the coronary arteries in Group 1 allografts. Group 2 allografts demonstrated abundant infiltration of collagenous fibers in the adventitia and intima of arteries and arterioles resulting in significant luminal stenosis. In contrast, pretreatment of animals with SPC and CP induced long-term allograft survival; myocardial fibrosis and CAV were dramatically reduced in Group 3 compared with Groups 1 and 2. The infiltration of collagenous fibers in coronary arteries was one of the major causes of CAV. Preconditioning of recipients with SPC followed by CP not only induced immune tolerance but also alleviated myocardial fibrosis and CAV in allografts.

Tranilast, an antifibrogenic agent, ameliorates a dietary rat model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is the progressive form of nonalcoholic fatty liver disease and is one of the most common liver diseases in the developed world. The histological findings of NASH are characterized by hepatic steatosis, inflammation, and fibrosis. However, an optimal treatment for NASH has not been established. Tranilast, N-(3',4'-dimethoxycinnamoyl)-anthranilic acid, is an antifibrogenic agent that inhibits the action of transforming growth factor beta (TGF-beta). This drug is used clinically for fibrogenesis-associated skin disorders including hypertrophic scars and scleroderma. TGF-beta plays a central role in the development of hepatic fibrosis, and tranilast may thus ameliorate the pathogenesis of NASH. We investigated the effects of tranilast using an established dietary animal model of NASH, obese diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats and nondiabetic control Long-Evans Tokushima Otsuka (LETO) rats fed a methionine-deficient and choline-deficient diet. Treatment with 2% tranilast (420 mg/kg/day) for 8 weeks prevented the development of hepatic fibrosis and the activation of stellate cells, and down-regulated the expression of genes for TGF-beta and TGF-beta-target molecules, including alpha1 procollagen and plasminogen activator-1. In addition, tranilast attenuated hepatic inflammation and Kupffer cell recruitment, and down-regulated the expression of tumor necrosis factor alpha. Unexpectedly, tranilast ameliorated hepatic steatosis and up-regulated the expression of genes involved in beta-oxidation, such as peroxisome proliferator-activated receptor alpha and carnitine O-palmitoyltransferase-1. Most of these effects were observed in LETO rats and OLETF rats, which suggest that the action of tranilast is mediated through the insulin resistance-independent pathway.

CONCLUSION

Our findings suggest that targeting TGF-beta with tranilast represents a new mode of therapy for NASH.

Graft coronary artery disease in murine cardiac allografts: proposal to meet the need for standardized assessment

BACKGROUND

Inconsistency exists in assessing the severity of graft coronary artery disease (GCAD) in studies that use mouse models. The central issue associated with this inconsistency is the lack of a standardized approach for assessing mouse GCAD.

METHODS

We propose a new histologic definition of GCAD based on 3 successive stages (endotheliitis, premature lesion, and mature lesion) that mark the progression of this condition. In addition to these qualitative measures of GCAD, we propose including 2 additional morphometric parameters (percentage of luminal narrowing and intima-to-media ratio) and a measure of distribution (percentage of affected vessels) in the routine quantification of GCAD.

RESULTS

We introduce 2 new mouse models of GCAD as examples that satisfy these criteria.

CONCLUSION

The proposed assessment criteria may simplify data collection and interpretation of results in various models of GCAD.

The angiotensin II type 1 receptor blocker valsartan attenuates graft vasculopathy

OBJECTIVE

Transplant arteriosclerosis remains the major cause of graft failure after cardiac transplantation. Here, we investigated the effects of the angiotensin II type 1 receptor blocker valsartan on the development of transplant arteriosclerosis in a murine model of cardiac transplantation.

METHODS

Hearts from DBA/2 (H-2(d)) mice were heterotopically transplanted into B10.D2 (H-2(d)) mice. Recipients were treated with oral administration of valsartan (10 mg/kg/day) or vehicle.

RESULTS

Morphometrical analysis of the cardiac allografts harvested at 30 days revealed that valsartan significantly reduced the development of coronary atherosclerosis (intima/media ratio: 0.39 +/- 0.05 vs. 0.66 +/- 0.08, P < 0.01). At two weeks after transplantation, there was no significant difference between the two groups in expression of adhesion molecules and cytokines. Valsartan significantly reduced the number of peripheral mononuclear cells that differentiated into smooth muscle-like cells in the presence of basic fibroblast growth factor and platelet-derived growth factor BB (18.0 +/- 1.5 vs. 30.3 +/- 4.4 cells/HPF, P = 0.01).

CONCLUSIONS

These results suggest that angiotensin II plays a role in the pathogenesis of transplant arteriosclerosis and that blockade of angiotensin II type 1 receptor might be effective as a prophylactic therapy for transplant arteriosclerosis along with conventional immunosuppressive drugs.

Antimonocyte Chemoattractant Protein-1 Gene Therapy Attenuates Graft Vasculopathy

Objective— Accelerated coronary arteriosclerosis remains a major problem in the long-term survival of cardiac transplant recipients. However, the pathogenesis of graft vasculopathy is poorly understood, and there is no effective therapy. Transplant arteriosclerosis is characterized by early mononuclear cell attachment on the transplanted vessel followed by development of concentric neointimal hyperplasia. Early and persistent expression of monocyte chemoattractant protein-1 (MCP-1) in cardiac allografts has been implicated for the pathogenesis of transplant arteriosclerosis.

Methods and Results— We investigated whether anti-MCP-1 gene therapy can inhibit the development of intima hyperplasia in a mouse model of cardiac transplantation. Either the dominant-negative form of MCP-1 (7ND) or control vector was transfected into the skeletal muscles of B10.D2 mice. Cardiac allografts from DBA/2 mice were transplanted heterotopically into B10.D2 mice. 7ND gene transfer was associated with a significant reduction of the number of mononuclear cells accumulating in the lumen of the graft coronary arteries at 1 week and an attenuation of the development of the lesion at 8 weeks (intima/media ratio 0.79±0.05 versus 0.48±0.04).

Conclusions— The MCP-1/chemokine receptor 2 (CCR2) signaling pathway plays a critical role in the pathogenesis of graft vasculopathy. This new anti-MCP-1 gene therapy might be useful to treat graft vascular disease.

Cancer, inflammation and the AT1 and AT2 receptors

The critical role of inappropriate inflammation is becoming accepted in many diseases that affect man, including cardiovascular diseases, inflammatory and autoimmune disorders, neurodegenerative conditions, infection and cancer.

This review proposes that cancer up-regulates the angiotensin II type 1 (AT1) receptor through systemic oxidative stress and hypoxia mechanisms, thereby triggering chronic inflammatory processes to remodel surrounding tissue and subdue the immune system. Based on current literature and clinical studies on angiotensin receptor inhibitors, the paper concludes that blockade of the AT1 receptor in synergy with cancer vaccines and anti-inflammatory agents should offer a therapy to regress most, if not all, solid tumours.

With regard to cancer being a systemic disease, an examination of supporting evidence for a systemic role of AT1 in relationship to inflammation in disease and injury is presented as a logical progression. The evidence suggests that regulation of the mutually antagonistic angiotensin II receptors (AT1 and AT2) is an essential process in the management of inflammation and wound recovery, and that it is an imbalance in the expression of these receptors that leads to disease.

In consideration of cancer induced immune suppression, it is further postulated that the inflammation associated with bacterial and viral infections, is also an evolved means of immune suppression by these pathogens and that the damage caused, although incidental, leads to the symptoms of disease and, in some cases, death.

It is anticipated that manipulation of the angiotensin system with existing anti-hypertensive drugs could provide a new approach to the treatment of many of the diseases that afflict mankind.

Tranilast inhibits cytokine-induced nuclear factor kappaB activation in vascular endothelial cells

Tranilast [N-(3,4-dimethoxycinnamoyl)anthranilic acid] inhibits vascular inflammation. However, the relevant anti-inflammatory mechanisms are not completely understood. We studied the effects of tranilast on nuclear factor-kappaB (NF-kappaB)-dependent endothelial cell adhesion molecule expression and transcriptional regulation. Cultured human umbilical vein endothelial cells were preincubated with 12.5 to 100 microg/ml tranilast. Tumor necrosis factor-alpha (TNF-alpha)-induced endothelial VCAM-1, ICAM-1, and E-selectin surface expression was inhibited dose dependently. Maximal inhibition achieved with 100 microg/ml tranilast was 38 +/- 6.9, 31.8 +/- 1.5, and 31.9 +/- 1.9%, respectively (mean +/- S.E.M., p < 0.001, n = 5). Secretion of interleukin 6, which is also NF-kappaB-sensitive, was significantly inhibited by tranilast. Endothelial MHC-I expression, which is independent of NF-kappaB, was not inhibited. Although cytokine-induced degradation of NF-kappaB inhibitor proteins (IkappaB-alpha, -beta, and -epsilon), nuclear translocation of NF-kappaB, and binding of NF-kappaB to kappaB cis-acting elements in the adhesion molecule promoters were not affected by tranilast, ICAM-1-kappaB and E-selectin-kappaB reporter gene activity was inhibited by 53% (n = 5, p < 0.01) and 51% (n = 5, p < 0.001), respectively. In contrast, using SP-1 and C/EBP constructs, reporter gene activity was not altered. Expression of the transcriptional coactivator cAMP response element binding protein binding protein (CBP) was inhibited by tranilast, resulting in a loss of interaction between NF-kappaB and CBP. Therefore, in therapeutically relevant concentrations (50 microg/ml), tranilast inhibits NF-kappaB-dependent transcriptional activation by interfering with the NF-kappaB/CBP association. We propose that inhibition of NF-kappaB dependent gene transcription contributes to the anti-inflammatory effects of tranilast.