Inhibition of collagen synthesis, smooth muscle cell proliferation, and injury-induced intimal hyperplasia by halofuginone

Pharmacotherapy of urethral stricture

Urethral stricture is characterized by the chronic formation of fibrous tissue, leading to the narrowing of the urethral lumen. Despite the availability of various endoscopic treatments, the recurrence of urethral strictures remains a common challenge. Postsurgery pharmacotherapy targeting tissue fibrosis is a promising option for reducing recurrence rates. Although drugs cannot replace surgery, they can be used as adjuvant therapies to improve outcomes. In this regard, many drugs have been proposed based on the mechanisms underlying the pathophysiology of urethral stricture. Ongoing studies have obtained substantial progress in treating urethral strictures, highlighting the potential for improved drug effectiveness through appropriate clinical delivery methods. Therefore, this review summarizes the latest researches on the mechanisms related to the pathophysiology of urethral stricture and the drugs to provide a theoretical basis and new insights for the effective use and future advancements in drug therapy for urethral stricture.

Halofuginone, a promising drug for treatment of pulmonary hypertension

BACKGROUND AND PURPOSE

Halofuginone is a febrifugine derivative originally isolated from Chinese traditional herb Chang Shan that exhibits anti-hypertrophic, anti-fibrotic and anti-proliferative effects. We sought to investigate whether halofuginone induced pulmonary vasodilation and attenuates chronic hypoxia-induced pulmonary hypertension (HPH).

EXPERIMENTAL APPROACH

Patch-clamp experiments were conducted to examine the activity of voltage-dependent Ca²⁺ channels (VDCCs) in pulmonary artery smooth muscle cells (PASMCs). Digital fluorescence microscopy was used to measure intracellular Ca²⁺ concentration in PASMCs. Isolated perfused and ventilated mouse lungs were used to measure pulmonary artery pressure (PAP). Mice exposed to hypoxia (10% O₂ ) for 4 weeks were used as model of HPH for in vivo experiments.

KEY RESULTS

Halofuginone increased voltage-gated K⁺ (K_v ) currents in PASMCs and K⁺ currents through KCNA5 channels in HEK cells transfected with KCNA5 gene. HF (0.03-1 μM) inhibited receptor-operated Ca²⁺ entry in HEK cells transfected with calcium-sensing receptor gene and attenuated store-operated Ca²⁺ entry in PASMCs. Acute (3-5 min) intrapulmonary application of halofuginone significantly and reversibly inhibited alveolar hypoxia-induced pulmonary vasoconstriction dose-dependently (0.1-10 μM). Intraperitoneal administration of halofuginone (0.3 mg·kg^-1 , for 2 weeks) partly reversed established PH in mice.

CONCLUSION AND IMPLICATIONS

Halofuginone is a potent pulmonary vasodilator by activating K_v channels and blocking VDCC and receptor-operated and store-operated Ca²⁺ channels in PASMCs. The therapeutic effect of halofuginone on experimental PH is probably due to combination of its vasodilator effects, via inhibition of excitation-contraction coupling and anti-proliferative effects, via inhibition of the PI3K/Akt/mTOR signalling pathway.

Design and characterization of a porous pouch to prevent peritoneal adhesions during in vivo vascular graft maturation

Vein grafts for coronary artery bypass are not available in more than 30% of patients due to prior use or systemic vascular diseases. Tissue engineered vascular grafts (TEVGs) have shown promise, but intimal hyperplasia and graft thrombosis are still concerns when grafted in small-diameter arteries. In this study, we utilized the peritoneal cavity as an "in vivo" bioreactor to recruit autologous cells to electrospun conduits enclosed within porous pouches to improve the response after grafting. Specifically, we designed a new poly (ethylene glycol)-based pouch to avoid adhesion to the peritoneal wall and still allow the necessary peritoneal fluid to reach the enclosed conduit. The pouch mechanics in compression and bending were determined through experiments and finite element simulations to optimize the pouch design. This included poly (ethylene glycol) concentration, pore density, and pouch size. We demonstrated that the optimized pouch was able to withstand the estimated forces applied in the rat peritoneal cavity and it allowed maturation of the enclosed electrospun conduit. This pouch significantly reduced peritoneal adhesion formation compared to polytetrafluoroethylene pouches that have been used previously, which overcomes this potential limitation to clinical translation. After aortic grafting of pre-conditioned conduits, patent grafts with limited intimal hyperplasia were observed. Overall, this study demonstrated a new pouch design that allows the in vivo bioreactor strategy to be used for vascular tissue engineering without the potential side effect of peritoneal adhesion formation.

Plant-Derived Products for Treatment of Vascular Intima Hyperplasia Selectively Inhibit Vascular Smooth Muscle Cell Functions

Natural products are used widely for preventing intimal hyperplasia (IH), a common cardiovascular disease. Four different cells initiate and progress IH, namely, vascular smooth muscle, adventitial and endothelial cells, and circulation or bone marrow-derived cells. Vascular smooth muscle cells (VSMCs) play a critical role in initiation and development of intimal thickening and formation of neointimal hyperplasia. In this review, we describe the different originating cells involved in vascular IH and emphasize the effect of different natural products on inhibiting abnormal cellular functions, such as VSMC proliferation and migration. We further present a classification for the different natural products like phenols, flavonoids, terpenes, and alkaloids that suppress VSMC growth. Abnormal VSMC physiology involves disturbance in MAPKs, PI3K/AKT, JAK-STAT, FAK, and NF-κB signal pathways. Most of the natural isolate studies have revealed G1/S phase of cell cycle arrest, decreased ROS production, induced cell apoptosis, restrained migration, and downregulated collagen deposition. It is necessary to screen optimal drugs from natural sources that preferentially inhibit VSMC rather than vascular endothelial cell growth to prevent early IH, restenosis following graft implantation, and atherosclerotic diseases.

Emodin as a selective proliferative inhibitor of vascular smooth muscle cells versus endothelial cells suppress arterial intima formation

A well-known natural anthraquinone "Emodin", has been proven to inhibit the proliferation of vascular smooth muscle cells (VSMCs). But the anti-proliferative effects of emodin on both VSMCs versus vascular endothelial cells (VECs) are still largely unknown. Herein, a comparative study for the evaluation of anti-proliferation effects of emodin on human VSMCs and VECs was designed. Various methodologies including MTS, EdU assay, FACS analysis, qRT-PCR and mitochondrial fluorescent probes were used for detecting cell viabilities, DNA synthesis rate, cell cycle, proliferation genes expression levels and mitochondrial activities, respectively. In addition, carotid arteries balloon injury was performed to evaluate the effects of emodin on intima hyperplasia (IH) and re-endothelialization. The emodin showed a dose-dependent (0.05 to 5 μM) inhibition of hVSMCs proliferation was quiet higher than hVECs in vitro. Conditioned culture media with a range of emodin concentrations (2.5, and 5 μM) reduced CDK1, Ki67, and E2F-1 gene expression, along with inhibition of mitochondrial activities in both hVSMCs and hVECs cells, while former remained highly sensitive. Emodin (10 mg/kg) was injected intraperitoneally for 2 weeks, and had obvious alleviation in an endothelial denudation induced-IH formation and limited interfere-endothelialization in injured arteries in vivo. Emodin preferentially inhibited hVSMCs proliferation but not the hVECs in vitro and had limited influence on the re-endothelialization of later in a rat artery endothelial denudation model. It is concluded that emodin will provide a promising approach for efficient prevention of blood vessel restenosis.

Nitinol-based nanotubular coatings for the modulation of human vascular cell function

In this study, we describe the synthesis of an upright nanotubular coating with discrete, exposed nanotubes on top of superelastic Nitinol via anodization and characterization of the surface elemental composition and nickel release rates. We demonstrate, for the first time, that this coating could improve re-endothelialization by increasing the cell spreading and migration of primary human aortic endothelial cells on Nitinol. We also show the potential for reducing neointimal hyperplasia by decreasing the proliferation and expression of collagen I and MMP-2 in primary human aortic smooth muscle cells (HASMC). Furthermore, we did not observe the nanotubular surface to induce inflammation through ICAM-1 expression in HASMC as compared to the flat control. This coating could be used to improve Nitinol stents by reducing restenosis rates and, given the extensive use of Nitinol in other implantable devices, act as a generalized coating strategy for other medical devices.

Halofuginone stimulates adaptive remodeling and preserves re-endothelialization in balloon-injured rat carotid arteries

BACKGROUND

Three major processes, constrictive vessel remodeling, intimal hyperplasia (IH), and retarded re-endothelialization, contribute to restenosis after vascular reconstructions. Clinically used drugs inhibit IH but delay re-endothelialization and also cause constrictive remodeling. Here we have examined halofuginone, an herbal derivative, for its beneficial effects on vessel remodeling and differential inhibition of IH versus re-endothelialization.

METHODS AND RESULTS

Two weeks after perivascular application to balloon-injured rat common carotid arteries, halofuginone versus vehicle (n=6 animals) enlarged luminal area 2.14-fold by increasing vessel size (adaptive remodeling; 123%), reducing IH (74.3%) without inhibiting re-endothelialization. Consistent with its positive effect on vessel expansion, halofuginone reduced collagen type 1 (but not type 3) production in injured arteries as well as that from adventitial fibroblasts in vitro. In support of its differential effects on IH versus re-endothelialization, halofuginone produced greater inhibition of vascular smooth muscle cell versus endothelial cell proliferation at concentrations ≈50 nmol/L. Furthermore, halofuginone at 50 nmol/L effectively blocked Smad3 phosphorylation in smooth muscle cells, which is known to promote smooth muscle cell proliferation, migration, and IH, but halofuginone had no effect on phospho-Smad3 in endothelial cells.

CONCLUSIONS

Periadventitial delivery of halofuginone dramatically increased lumen patency via adaptive remodeling and selective inhibition of IH without affecting endothelium recovery. Halofuginone is the first reported small molecule that has favorable effects on all 3 major processes involved in restenosis.

Uterine fibroids: clinical manifestations and contemporary management

Uterine fibroids (leiomyomata) are extremely common lesions that are associated with detrimental effects including infertility and abnormal uterine bleeding. Fibroids cause molecular changes at the level of endometrium. Abnormal regulation of growth factors and cytokines in fibroid cells may contribute to negative endometrial effects. Understanding of fibroid biology has greatly increased over the last decade. Although the current armamentarium of Food and Drug Administration-approved medical therapies is limited, there are medications approved for use in heavy menstrual bleeding that can be used for the medical management of fibroids. Emergence of the role of growth factors in pathophysiology of fibroids has led researchers to develop novel therapeutics. Despite advances in medical therapies, surgical management remains a mainstay of fibroid treatment. Destruction of fibroids by interventional radiological procedures provides other effective treatments. Further experimental studies and clinical trials are required to determine which therapies will provide the greatest benefits to patients with fibroids.

The antifibrotic drug halofuginone reduces ischemia/reperfusion-induced oxidative renal damage in rats

AIM

The objective of the present study was to evaluate the protective effects of halofuginone against renal ischemia/reperfusion (I/R) injury.

MATERIALS AND METHODS

Male Wistar albino rats were unilaterally nephrectomized and the left renal pedicles were occluded for 45 min to induce ischemia and then reperfused for 6 h (early) or for 72 h (late). The rats were treated intraperitoneally with either halofuginone (100 μg/kg/day) or saline 30 min prior to ischemia and the dose was repeated in the late reperfusion groups. In the sham groups, rats underwent unilateral nephrectomy and were treated at similar time points. The animals were decapitated at either 6 h or 72 h of reperfusion and trunk blood and kidney samples were obtained.

RESULTS

I/R injury increased renal malondialdehyde levels, myeloperoxidase activity and reactive oxygen radical levels, and decreased the renal glutathione content. Halofuginone treatment was found to reduce oxidative I/R injury and improve renal function in the rat kidney, as evidenced by reduced generation of reactive oxygen species, depressed lipid peroxidation and myeloperoxidase activity, and increased glutathione levels.

CONCLUSIONS

The present findings demonstrate the anti-inflammatory and antioxidant effects of halofuginone in renal I/R injury, supporting its potential use where renal I/R injury is inevitable.

Scleroderma therapy: clinical overview of current trends and future perspective

Systemic sclerosis is a chronic autoimmune condition with a complex pathogenesis and a high rate of mortality and morbidity. Internal organ involvement requires interdisciplinary approach in individual patient management. New discoveries in the pathogenesis of scleroderma herald a drastic change in the traditional outlook to therapy and have led to the development of the target-based approach in management. The challenge at present is to translate these advances in molecular mechanisms into well-designed clinical trials that will recognize potential disease-modifying therapies. This article is an evidence-based review of prevailing treatment options and future therapeutic targets in systemic sclerosis.

Temporal network based analysis of cell specific vein graft transcriptome defines key pathways and hub genes in implantation injury

Vein graft failure occurs between 1 and 6 months after implantation due to obstructive intimal hyperplasia, related in part to implantation injury. The cell-specific and temporal response of the transcriptome to vein graft implantation injury was determined by transcriptional profiling of laser capture microdissected endothelial cells (EC) and medial smooth muscle cells (SMC) from canine vein grafts, 2 hours (H) to 30 days (D) following surgery. Our results demonstrate a robust genomic response beginning at 2 H, peaking at 12-24 H, declining by 7 D, and resolving by 30 D. Gene ontology and pathway analyses of differentially expressed genes indicated that implantation injury affects inflammatory and immune responses, apoptosis, mitosis, and extracellular matrix reorganization in both cell types. Through backpropagation an integrated network was built, starting with genes differentially expressed at 30 D, followed by adding upstream interactive genes from each prior time-point. This identified significant enrichment of IL-6, IL-8, NF-κB, dendritic cell maturation, glucocorticoid receptor, and Triggering Receptor Expressed on Myeloid Cells (TREM-1) signaling, as well as PPARα activation pathways in graft EC and SMC. Interactive network-based analyses identified IL-6, IL-8, IL-1α, and Insulin Receptor (INSR) as focus hub genes within these pathways. Real-time PCR was used for the validation of two of these genes: IL-6 and IL-8, in addition to Collagen 11A1 (COL11A1), a cornerstone of the backpropagation. In conclusion, these results establish causality relationships clarifying the pathogenesis of vein graft implantation injury, and identifying novel targets for its prevention.

Phase II AIDS Malignancy Consortium trial of topical halofuginone in AIDS-related Kaposi sarcoma

Using a novel blinded intrapatient vehicle control design, we conducted a phase II study of topically administered halofuginone, an angiogenesis inhibitor that inhibits collagen type-I and matrix metalloproteinases (MMPs), in patients with AIDS-related Kaposi sarcoma. Serial Kaposi sarcoma biopsies assessed treatment effects on angiogenic factors and Kaposi sarcoma herpesvirus-latency associated nuclear antigen-1 (KSHV-LANA). We observed marked heterogeneity of KSHV-LANA expression. Although the small number of subjects whose response could be evaluated precluded definitive assessment of halofuginone's efficacy, we observed a significant decrease in type-I collagen only in halofuginone-treated lesions, but no effect on MMP-2. The trial design is applicable to future studies of topical agents.

Halofuginone, a specific inhibitor of collagen type 1 synthesis, ameliorates oxidant colonic damage in rats with experimental colitis

To evaluate the effect of halofuginone on trinitrobenzene sulfonic acid (TNBS)-induced colonic injury, rats were given halofuginone (40 microg/kg, intraperitoneally) or saline 1 h before the induction of colitis, and the injections were continued twice daily for 3 days until they were decapitated. High macroscopic and microscopic damage scores, elevated colonic wet weights, colonic myeloperoxidase activity, malondialdehyde and tissue collagen level, and luminol chemiluminescence values, and marked reduction in glutathione level of the saline-treated colitis group were all reversed by treatment with halofuginone. In conclusion, halofuginone exerts beneficial effects in TNBS-induced colonic inflammation in rats. The anti-inflammatory effects of halofuginone appear to involve suppression of neutrophil accumulation, preservation of endogenous glutathione, and inhibition of reactive oxidant generation. Halofuginone also shows antifibrotic effect via inhibition of tissue collagen production. The present data encourage possible use of the antifibrotic halofuginone as an anti-inflammatory agent in improving oxidative injury in colitis.

PPARgamma enhances IFNgamma-mediated transcription and rescues the TGFbeta antagonism by stimulating CIITA in vascular smooth muscle cells

Chronic inflammatory response and active vascular remodeling are two featured pathophysiological events during atherogenesis. Gamma interferon (IFN-gamma) modulates these two processes through transcriptional control of major histocompatibility complex II (MHC II) and collagen type I (COL1A2) genes, mediated by class II transactivator (CIITA). Transforming growth factor (TGF-beta) antagonizes the effect of IFN-gamma in part by dampening the expression of CIITA. Here we report that peroxisome proliferator activated receptor gamma (PPARgamma) enhanced MHC II activation and COL1A2 repression by IFN-gamma while rescuing the antagonism by TGF-beta in a CIITA-dependent manner in human aortic smooth muscle cells judged by quantitative PCR and luciferase reporter assays. PPARgamma exerted its effect by augmenting the levels of CIITA and stimulating CIITA recruitment to target promoters as evidenced by chromatin immunoprecipitation assays. The up-regulation of CIITA levels was the result of PPARgamma-mediated transcriptional activation of CIITA through promoter IV, and increased CIITA protein stability. Thus, our data suggest that PPARgamma could be a key factor in fine-tuning inflammation as well as restructuring of vessel walls during atherogenesis by acting as a "balance tipper" of the differential effects exerted by cytokines.

Regulation of arterial remodeling and angiogenesis by urokinase-type plasminogen activatorThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue)

A wide variety of disorders are associated with an imbalance in the plasminogen activator system, including inflammatory diseases, atherosclerosis, intimal hyperplasia, the response mechanism to vascular injury, and restenosis. Urokinase-type plasminogen activator (uPA) is a multifunctional protein that in addition to its fibrinolytic and matrix degradation capabilities also affects growth factor bioavailability, cytokine modulation, receptor shedding, cell migration and proliferation, phenotypic modulation, protein expression, and cascade activation of proteases, inhibitors, receptors, and modulators. uPA is the crucial protein for neointimal growth and vascular remodeling. Moreover, it was recently shown to be implicated in the stimulation of angiogenesis, which makes it a promising multipurpose therapeutic target. This review is focused on the mechanisms by which uPA can regulate arterial remodeling, angiogenesis, and cell migration and proliferation after arterial injury and the means by which it modulates gene expression in vascular cells. The role of domain specificity of urokinase in these processes is also discussed.

Effectiveness of topically applied halofuginone in management of subglottic stenosis in rats

OBJECTIVE

The aim of the study is to ascertain the antifibrotic effect of topically applied halofuginone after acute subglottic injury.

MATERIALS AND METHODS

After standardized trauma to subglottic area, rats were divided into two groups: the study group that received treatment and the control group that did not. The subjects were treated with topical application of cottonoid soaked in 30 mg/dL halofuginone solution for 5 minutes after subglottic trauma. The larynx specimens were examined histopathologically by light microscopy to assess fibrosis, epithelialization, inflammation, and necrosis.

RESULTS

The fibrosis indexes of the treated group were significantly less than those of the control group (P < 0.05).

CONCLUSIONS

Topically applied halofuginone hydrobromide decreases fibrosis/scar tissue formation secondary to experimentally induced acute subglottic trauma.

The antifibrotic drug halofuginone inhibits proliferation and collagen production by human leiomyoma and myometrial smooth muscle cells

OBJECTIVE

To investigate the effects of the antifibrotic drug halofuginone on extracellular matrix production, cell proliferation, and apoptosis of cultured myometrial and leiomyoma smooth muscle cells.

DESIGN

Comparative and controlled experimental research study.

SETTING

University research laboratory.

PATIENT(S)

Leiomyoma and myometrial tissues were obtained from eight different patients at the time of elective hysterectomy.

MAIN OUTCOME MEASURE(S)

The effects of halofuginone on cell proliferation were assessed by tritiated thymidine uptake assays and cell count assays. Effects on TGFbeta1, collagen type I, and collagen type III mRNA levels were assessed by quantitative real-time polymerase chain reaction. Effects on apoptosis were assayed using a chemiluminescent assay to measure changes in caspase 3 and 7.

RESULT(S)

Halofuginone inhibited cell proliferation of both leiomyoma and autologous myometrial cells in a dose-dependent manner by inhibiting DNA synthesis within 24 hours and later inducing apoptosis (as measured by increased caspase 3/7) by 48-72 hours. Halofuginone also significantly reduced collagen type I (alpha1) and collagen type III (alpha1) mRNA levels, as well as the profibrotic factor TGFbeta1 mRNA levels in both cell types.

CONCLUSION(S)

These results provide evidence to support the use of the antifibrotic drug halofuginone as a novel drug treatment for uterine leiomyomas.

An organotypical in vitro model for vascular tissue remodelling and its application to study radiation effects

An organotypic in vitro model, to study vascular tissueremodeling, was evaluated as a function of culture period. Inorder to validate the model as a tool for studying vascularresponses to damage, a dose-response analysis to ionizingirradiation was included.Rat aortic rings were explanted in vitro after being irradiatedwith single doses of (60)Co gamma-rays, namely 0, 5, 10, 15, 20or 25 Gy. Irradiated and sham-irradiated aortic rings werecultured for 3 weeks. Explant outgrowth on an adhesivesubstrate was evaluated by macroscopical scoring, and ringsderived from each irradiation group together with theoutgrowths were fixed and embedded in paraffin after 2, 7, 14and 21 days. Bromodeoxyuridine incorporation, alpha smoothmuscle actin and collagen types I and III were scored onimmunohistochemically stained sections. For each studiedparameter, irradiated and sham-irradiated rings were compared.In cultures of sham-irradiated rings, alterations from acontractile towards a synthetic/migratory smooth muscle cellphenotype were confirmed. After 3 weeks, fullgrown cultures hadformed. Irradiation slowed down the phenotypical modifications.After 15 Gy, irradiation explant outgrowth was already retarded;after 25 Gy, the outgrowth was completely blocked. On the otherhand, a dose of 15 Gy or more induced an increased collagen Iproduction in the tunica media.In conclusion, the present organotypical in vitro model fits toanalyse dynamics in the original vascular tissues as well as inthe primary outgrowth. It enables to confirm features oftissular reorganization and effects of ionizing radiationdescribed in vivo.

Type I collagen expression contributes to angiogenesis and the development of deeply invasive cutaneous melanoma

Tumors are complex tissues composed of neoplastic cells, soluble and insoluble matrix components and stromal cells. Here we report that in melanoma, turn-over of type I collagen (Col(I)), the predominant matrix protein in dermal stroma affects melanoma progression. Fibroblasts juxtaposed to melanoma cell nests within the papillary dermis display high levels of Col(I) mRNA expression. These nests are enveloped by collagen fibers. In contrast, melanoma-associated fibroblasts within the reticular dermis express Col(I) mRNA at a level that is comparable to its expression in uninvolved dermis and reduced amount of collagen protein can be observed. To determine the significance of Col(I) expression in melanoma, we pharmacologically inhibited its transcription in a porcine cutaneous melanoma model by oral administration of halofuginone. When administered before melanoma development, it reduced melanoma incidence and diminished the transition from microinvasive toward deeply invasive growth by limiting the development of a tumor vasculature. Whereas invasive melanoma growth has been correlated with increased blood vessel density previously, our data for the first time demonstrate that the proangiogenic effect of Col(I) expression by fibroblasts and vascular cells precedes the development of invasive melanomas in a de novo tumor model.

Phase I and pharmacokinetic study of halofuginone, an oral quinazolinone derivative in patients with advanced solid tumours

PURPOSE

Halofuginone (tempostatin) is a synthetic derivative of a quinazolinone alkaloid showing anti-angiogenic, anti-metastatic and anti-proliferative effects in preclinical studies. The objectives of this phase I study were to assess the dose-limiting toxicities (DLTs), to determine the maximum tolerated dose (MTD) and to study the pharmacokinetics (PKs) of halofuginone when administered once or twice daily orally to patients with advanced solid tumours.

METHODS

Patients were treated with escalating doses of halofuginone at doses ranging from 0.5 to 3.5 mg/day. For pharmacokinetic analysis plasma sampling was performed during the first and second course and assayed using a validated high-performance liquid chromatographic assay with mass spectrometric detection.

RESULTS

Twenty-four patients received a total of 106 courses. The 'acute' MTD was reached at 3.5 mg/day, with nausea, vomiting, and fatigue as DLT. The recommended dose for chronic administration was defined as 0.5mg/day with the requirement of 5HT3 antagonists to control nausea and vomiting considered as DLT. Several patients experienced bleeding complications on treatment with halofuginone in which a causal relationship could not be excluded. The PKs of halofuginone were linear over the dose range studied with a large interpatient variability.

CONCLUSIONS

In this study the DLT of halofuginone was nausea, vomiting, and fatigue. The recommended dose for phase II studies of halofuginone is 0.5mg administered orally, once daily.

Halofuginone induces matrix metalloproteinases in rat hepatic stellate cells via activation of p38 and NFkappaB

The semisynthetic plant alkaloid halofuginone (HAL) was reported to prevent and partly reverse experimental liver fibrosis. However, its mechanisms of action are poorly understood. We therefore aimed to determine the antifibrotic potential of HAL and to characterize involved signal transduction pathways in hepatic stellate cells (HSCs). Results were compared with its in vivo effects in a rat model of reversal of established liver fibrosis induced by thioacetamide. In vitro HAL inhibited HSC proliferation and migration dose dependently at submicromolar concentrations. HAL (200 nm) up-regulated matrix metalloproteinase (MMP)-3 and MMP-13 expression between 10- and 50-fold, resulting in a 2- to 3-fold increase of interstitial collagenase activity. Procollagen alpha1(I) and MMP-2 transcript levels were suppressed 2- to 3-fold, whereas expression of other profibrogenic mRNAs remained unaffected. p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor kappaB(NFkappaB) pathways were activated by HAL, and specific inhibitors of p38 MAPK and NFkappaB dose dependently inhibited MMP-13 induction. Treatment with HAL did not affect HSC viability, and observed effects were reversible after its removal. In vivo HAL up-regulated MMP-3 and -13 mRNA expression 1.5- and 2-fold, respectively, in cirrhotic rats, whereas tissue inhibitor of metalloproteinase-1 was suppressed by 50%. In conclusion, submicromolar concentrations of HAL inhibit HSC proliferation and migration and up-regulate their expression of fibrolytic MMP-3 and -13 via activation of p38 MAPK and NFkappaB. The remarkable induction of MMP-3 and -13 makes HAL a promising agent for antifibrotic combination therapies.

Pharmacological treatment for prevention of restenosis

Coronary artery disease (CAD) is the leading cause of mortality and morbidity among adults in the Western world. Coronary artery bypass grafting and percutaneous coronary interventions (PCI) have gained widespread acceptance for the treatment of symptomatic CAD. There has been an explosive growth worldwide in the utilisation of PCI, such as balloon angioplasty and stenting, which now accounts for over 50% of coronary revascularisation. Despite the popularity of PCI, the problem of recurrent narrowing of the dilated artery (restenosis) continues to vex investigators. In recent years, significant advances have occurred in the understanding of restenosis. Two processes seem to contribute to restenosis: remodelling (vessel size changes) and intimal hyperplasia (vascular smooth muscle cell [VSMC] proliferation and extracellular matrix [ECM] deposition). Despite considerable efforts, pharmacological approaches to decrease restenosis have been largely unsuccessful and the only currently applied modality to reduce the restenosis rate is stenting. However, stenting only prevents remodelling and does not inhibit intimal hyperplasia. Several potential targets for inhibiting restenosis are currently under investigation including platelet activation, the coagulation cascade, VSMC proliferation and migration, and ECM synthesis. In addition, new approaches for local drug therapy, such as drug eluting stents, are currently being evaluated in preclinical and clinical studies. In this article, we critically review the current status of drugs that are being evaluated for restenosis at various stages of development (in vitro, preclinical animal models and human trials).

Halofuginone Inhibits Serum-Stimulated Pericardial Tissue Retraction in Vitro

We developed an in vitro model of tissue contraction in which living pericardium, in response to serum, contracted and the cells in situ expressed proliferating cell nuclear antigen (PCNA) and synthesized collagen. Here we evaluated the effects of halofuginone on these serum-stimulated pericardial tissue responses. Parietal pericardium was incubated with media containing increasing doses of halofuginone and evaluated for tissue contraction, evident by tissue curling. Proliferation was measured by MTS metabolism and PCNA expression. Furthermore, collagen synthesis was compared between samples incubated with halofuginone, cytochalasin B, cytochalasin D, aphidicolin, or cytosine arabinoside (AraC), using Masson's trichrome and the monoclonal antibody to sheep type I procollagen, SP1. D8. Halofuginone inhibited tissue contraction, cellular proliferation, and collagen synthesis in a dose-dependent manner. In contrast, cytochalasin B, cytochalasin D, aphidicolin, and AraC, shown previously to prevent cellular proliferation, did not prevent type I collagen synthesis. Halofuginone has been implicated as an agent in the prevention of wound-healing fibrosis. This study suggests that halofuginone may have an added benefit in the inhibition of pericardial tissue contraction, which appeared to be related to the synthesis of type I procollagen.

Suppression of hepatocellular carcinoma growth in mice by the alkaloid coccidiostat halofuginone

Halofuginone, a widely used alkaloid coccidiostat, is a potent inhibitor of collagen alpha 1 (I) and matrix metalloproteinase 2 gene expression. Halofuginone also suppresses extracellular matrix deposition and fibroblast proliferation. It was recently shown to be effective in suppression of bladder carcinoma and glioma. This study sought to evaluate the effect of treatment with halofuginone on growth of hepatocellular carcinoma (HCC) in mice. Athymic Balb/c mice were injected subcutaneously with 10(7) human hepatoma cells (Hep3B), followed by treatment with halofuginone administered in the diet (750 microg/kg) starting on day 3, before tumour innoculation. The control group was received a normal diet. Mice were followed for survival, tumour volume and serum alpha-fetoprotein (alpha FP). The mechanism of the anti-tumour effect of halofuginone was determined in vitro by assessing tumour cell growth, and by measuring the serum concentrations of interferon-gamma (IFN gamma) and interleukin 2 (IL2). Halofuginone treatment induced almost complete tumour suppression in treated mice. Mortality rates were 10% and 50%, in halofuginone-treated and control mice, respectively (P<0.001). No visible tumour was observed in treated mice, as compared with a 364 mm3 tumour in control mice. Serum alpha FP were 0.1 and 212 ng/ml in treated and control mice, respectively (P<0.005). Halofuginone significantly inhibited HCC proliferation in vitro. Maximal inhibition of 64% of tumour cell growth was observed at a concentration of 10(-8) M. The anti-tumour effect was mediated via a significant increase in IFN gamma and IL2 (90 vs. 35, and 210 vs. 34 pg/ml in treated and control groups, respectively, P<0.005). Treatment with halofuginone effectively suppressed the progression of HCC in mice. This effect may be associated with a direct anti-tumour effect, and/or enhancement of a systemic immune response.

Gamma-irradiation modulates vascular smooth muscle cell and extracellular matrix function: Implications for neointimal development

OBJECTIVE

Migration of vascular smooth muscle cells (SMCs) into the subintimal space, and their proliferation and resultant deposition of extracellular matrix are key processes in the development of intimal hyperplasia, leading to vascular recurrent stenosis. The purpose of this study was to investigate the effects of clinically administered doses of gamma-radiation on SMCs and extracellular matrix proteins in vitro, to better understand how it impinges on cellular and extracellular components of recurrent stenosis.

METHODS

The effects of gamma-irradiation (10, 20 Gy) on SMC migration into three-dimensional collagen matrix gels was quantitated by calibrated light microscopy, and the release of metalloproteinases into conditioned media was investigated with an enzyme-linked immunosorbent assay and zymography. Collagen production was assayed with [(3)H]-proline incorporation, and SMC phenotype changes with confocal microscopy with a fluorescent alpha-actin antibody. The effect of gamma-irradiation on extracellular matrix was investigated by quantitating untreated SMC proliferation ((3)H-thymidine incorporation) on irradiated endothelial cell-derived matrix and by assessing structural collagen matrix changes with sodium dodecylsulfate polyacrylamide gel electrophoresis. All groups were compared with nonirradiated control groups.

RESULTS

SMC vertical migration was significantly decreased by gamma-irradiation (48% and 55%, respectively; P <.0001). Irradiation did not generate measurable matrix protein crosslinks, nor did it alter the production of metalloproteinases or collagen synthesis. However, gamma-irradiation decreased the ability of extracellular matrix to induce nonirradiated SMC proliferation (15% reduction; P =.0028). Moreover, gamma-irradiation reversed the secretory phenotype of cultured SMCs to a contractile type.

CONCLUSIONS

The gamma-irradiation-induced reduction of cellular migration, changes in SMC phenotype, and functional activity of matrix-bound factors, and no measurable effects on the production of extracellular matrix proteins, may in part explain the diverse effects of gamma-irradiation on the restenotic response.

Eosinophil major basic protein: first identified natural heparanase-inhibiting protein

BACKGROUND

Heparanase and eosinophils are involved in several diseases, including inflammation, cancer, and angiogenesis.

OBJECTIVE

We sought to determine whether eosinophils produce active heparanase.

METHODS

Human peripheral blood eosinophils were isolated by immunoselection and tested for heparanase protein (immunocytochemistry, Western blot), mRNA (RT-PCR) and activity (Na(2)[(35)S]O(4)-labeled extracellular matrix degradation) before and after activation. Heparanase intracellular localization (confocal laser microscopy) and ability to bind to eosinophil major basic protein (MBP) were also evaluated (immunoprecipitation). A model of allergic peritonitis resulting in eosinophilia was induced in TNF knockout and wild-type mice for in vivo studies.

RESULTS

Eosinophils synthesized heparanase mRNA and contained heparanase in the active (50-kd) and latent (65-kd) forms. Heparanase partially co-localized with and was bound to MBP. No heparanase enzymatic activity was detected in eosinophils resting or activated with various agonists, including GM-CSF/C5a. Eosinophil lysates and MBP inhibited recombinant heparanase activity in a concentration-dependent manner (100%, 2 x 10(-7) mol/L). Eosinophil peroxidase and eosinophil cationic protein, but not myelin basic protein or compound 48/80, partially inhibited heparanase activity. Poly-l-arginine at very high concentrations caused an almost complete inhibition. In allergic peritonitis, heparanase activity in the peritoneal fluid inversely correlated with eosinophil number.

CONCLUSIONS

MBP is the first identified natural heparanase-inhibiting protein. Its presence in the eosinophil granules might indicate a protective function of these cells in diseases associated with inflammation and cancer progression.

Arterial wall strength after endovascular photodynamic therapy

BACKGROUND AND OBJECTIVES

Vascular photodynamic therapy (PDT) inhibits intimal hyperplasia (IH) induced by angioplasty in rat iliac arteries by eradicating the proliferating smooth muscle cells. This process may jeopardise the structure and strength of the arterial wall, reflected by a decreased bursting pressure.

STUDY DESIGN/MATERIALS AND METHODS

Thirty male Wistar rats of 250-300 g were subdivided into 3 groups (n = 10). In all groups, IH was induced by balloon injury (BI). One experimental group received PDT at 50 J/cm diffuser length, the other group at 100 J/cm diffuser length. The third group served as control group and received no PDT. In half of each group the bursting pressure was analyzed after 2 hours (n = 5), in the other half after 1 year.

RESULTS

Two hours after the procedure the bursting pressure was 3.37 +/- 0.58 (+/-SEM) bar in the BI + PDT 50 and 3.96 +/- 0.43 bar in the BI + PDT 100 group, compared to 2.20 +/- 0.27 bar in the BI group (P < 0.05). After 1 year these values were 3.18 +/- 0.87 bar in the BI + PDT 50 (P < 0.05) and 2.02 +/- 0.31 bar in the BI + PDT 100 group, compared to 2.10 +/- 0.30 bar in the BI group (NS). In the BI + PDT 100 group, 3 out of 5 rats appeared to have aneurysmal dilatation after 1 year.

CONCLUSIONS

Endovascular PDT increases the arterial wall strength as measured by the bursting pressure at short-term. After 1 year, wall strength is not diminished as measured by bursting pressure, but aneurysmal dilatation nevertheless developed with 100 J/cm. dl. This may limit the use of high energy PDT.

The Use of Halofuginone in Limiting Urethral Stricture Formation and Recurrence: An Experimental Study in Rabbits

PURPOSE

We developed a reproducible animal model for the induction of urethral stricture in the rabbit and evaluated the role of halofuginone in limiting stricture formation.

MATERIALS AND METHODS

A total of 20 New Zealand male rabbits were used in the first phase of the experiment. Bulbar urethral stricture was induced by electrocoagulation. The animals were then randomly assigned to 2 groups of 10 each, which received a diet containing halofuginone or a normal diet. In the second phase electrocoagulation induced stricture was treated with visual internal urethrotomy in 45 rabbits. These rabbits were randomly assigned to 2 groups, namely a halofuginone and a control group.

RESULTS

In the first phase stricture developed in 2 study rabbits (20%) vs 10 controls (100%). In the second phase 37 rabbits were evaluable (8 died). Recurrent stricture was observed in 5 of the 18 study rabbits (27%) vs 14 of the 19 controls (73%).

CONCLUSIONS

Halofuginone is effective in limiting the occurrence of de novo urethral stricture and recurrent stricture after visual internal urethrotomy. This antifibrotic molecule may become an important therapy to treat urethral stricture and/or recurrence following endoscopic manipulation of stricture in humans.

Halofuginone to treat fibrosis in chronic graft-versus-host disease and scleroderma

Chronic graft-versus-host disease (cGvHD) and systemic sclerosis (scleroderma [SSc]) share clinical characteristics, including skin and internal organ fibrosis. Fibrosis, regardless of the cause, is characterized by extracellular matrix deposition, of which collagen type I is the major constituent. The progressive accumulation of connective tissue results in destruction of normal tissue architecture and internal organ failure. In both SSc and cGvHD, the severity of skin and internal organ fibrosis correlates with the clinical course of the disease. Thus, there is an unmet need for well-tolerated antifibrotic therapy. Halofuginone is an inhibitor of collagen type I synthesis in cells derived from various tissues and species and in animal models of fibrosis in which excess collagen is the hallmark of the disease. Halofuginone decreased collagen synthesis in the tight skin mouse (Tsk) and murine cGvHD, the 2 experimental systems that show many features resembling those of human GvHD. Inhibition of collagen synthesis by halofuginone is achieved by inhibiting transforming growth factor beta-dependent Smad3 phosphorylation. Dermal application of halofuginone caused a decrease in collagen content at the treated site of a cGvHD patient, and reduction in skin scores was observed in a pilot study with SSc patients. The results of the human studies provide basis for using halofuginone treatment for dermal fibrosis. As a first step toward future treatment of internal organ involvement, an oral administration study was performed in which halofuginone was well tolerated and plasma levels surpassed the predicted therapeutic exposure.

Adrenomedullin gene delivery inhibits neointima formation in rat artery after balloon angioplasty

Adrenomedullin (AM) is a potent vasodilator expressed in tissues relevant to cardiovascular function. AM peptide has been shown to inhibit the proliferation and migration of vascular smooth muscle cells in vitro. However, the effect of AM on blood vessels after vascular injury in vivo has not been elucidated. In order to explore the potential roles of AM in vascular biology, we evaluated the effect of AM by local gene delivery on neointima formation in balloon-injured rat artery. Adenovirus carrying the human AM cDNA under the control of cytomegalovirus promoter/enhancer (Ad.CMV-hAM) was generated by homologous recombination. After delivery of Ad.CMV-hAM into rat left carotid artery, we identified the expression of human AM mRNA in the left carotid artery, but not in the right carotid artery, heart or kidney by reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot analysis. Following local AM gene delivery, we observed a 51% reduction in intima/media ratio at the injured site as compared with that of control rats injected with the luciferase gene (n=7, P<0.01). AM gene transfer resulted in regeneration of endothelium as compared to the control. AM gene delivery significantly increased cGMP levels in balloon-injured arteries. These results indicate that AM contributes to reduction of neointima formation by promotion of re-endothelialization and inhibition of vascular smooth muscle cell proliferation via cGMP-dependent signaling pathway.

Slowed progression or elimination of atherosclerosis by low-frequency electrical impulses

BACKGROUND

In our previous investigations we showed that electrical impulses (EI) can prevent the development of atherosclerosis if they began simultaneously with high cholesterol diet (HCD) or in the early stages of atherosclerosis (after three weeks of HCD only). In this investigation we demonstrated the slow progression or elimination of atherosclerosis by low-frequency EI in case of moderate atherosclerosis (after eight weeks of HCD).

METHODS

Series I rabbits (control group) were fed HCD for eight weeks. Series II rabbits were fed HCD for eight weeks and were then switched to normal diet for eight weeks (no EI). Series III rabbits were fed HCD for eight weeks and then switched to a normal diet with simultaneous EI (applied near the abdominal aorta) for eight weeks (3 V, 30 single impulses per minute, 24 hours/day). After euthanization, the level of atherosclerosis, percentage of surface area involved in the atherosclerosis process, and an atherosclerosis score were calculated in the aortic arch, thoracic and abdominal aorta.

RESULTS

Statistically significant differences were seen in the level of atherosclerosis in the abdominal aorta between series III animals (0.4 +/- 0.2) and the other two groups: 1.5 +/- 0.4 in series I (HCD only), 1.2 +/- 0.3 in series II (HCD then normal diet). Gross examination of the surface also revealed statistically significant differences (p < 0.05) in the percentage of atherosclerosis between the control series I (30.1 +/- 4.1%) and series II (21.3 +/- 3.6%), compared with series III (5.5 +/- 5.4%). In addition, the atherosclerosis score was also significantly different: 45.8 +/- 3.9 in series I, 25.2 +/- 6.9 in series II, and 2.2 +/- 2.0 in series III (p < 0.05).

CONCLUSION

Our study showed that, when applied near the abdominal aorta, low-frequency electrical impulses decrease atherosclerotic deposition in the abdominal aorta.

Cytokine directed therapy in scleroderma: rationale, current status, and the future

The hallmark of scleroderma is cutaneous and visceral fibrosis characterized and by increased biosynthesis of multiple matrix proteins by interstitial fibroblasts. Studies over recent years have delineated pathways involved in promoting matrix synthesis and elucidated the molecular pathways of regulation. Central to the regulation of fibrosis are extracellular mediators, called cytokines, which are elaborated by a variety of cells, including those in the immune system, vascular cells, and fibroblasts themselves. The concept that inhibiting or promoting the action of these naturally occurring profibrotic or antifibrotic molecules, respectively, is a rational therapeutic approach to treating scleroderma and other fibrotic diseases finds support in animal studies and anticytokine therapy conducted in relation to rheumatoid arthritis and other disorders. This review looks at cytokines known or thought to play a role in scleroderma and/or other fibrotic states and at potential therapy directed at these mediators. Potential targets for therapy include transforming growth factor beta (TGF-beta), connective tissue growth factor (CTGF), IL-4, IL-13, MCP-1, and endothelin, among others.

Biochemical analysis of collagen and elastin synthesis in the balloon injured rat carotid artery

INTRODUCTION

Balloon catheter denudation of the endothelium in the common carotid artery of the rat is routinely used as a model of neointimal lesion development. The response to endothelial denuding injury involves proliferation and migration of medial smooth muscle cells (SMCs), with the formation of a dramatically thickened neointima. While many studies have focused on the kinetics of the early proliferative and migration responses, much less attention has been paid to the pronounced accumulation of extracellular matrix that occurs as the neointima grows. The purpose of this study was to measure collagen and elastin content, and to assess collagen and elastin synthesis in injured rat carotid arteries.

METHODS

Male Sprague-Dawley rats were subject to balloon catheter injury of the left carotid artery using a 2F embolectomy catheter. Rats were sacrificed at different time points after injury, and both carotids left (injured) and right (uninjured and control) were used for measurement of elastin and collagen synthesis (7 days) and content (7, 21 and 60 days).

RESULTS

Elastin and collagen syntheses were significantly increased in the injured carotids at 7 days after injury. The increase in elastin synthesis was more dramatic (100% compared to control) than the increase in collagen synthesis (50% compared to control). Both elastin and collagen content were significantly increased by 21 days, and contents were further increased by 60 days in the injured carotid compared to uninjured controls. At 60 days, collagen content of the injured vessels was 2.09+/-0.01 mg/arterial segment compared to 1.32+/-0.08 mg/arterial segment in controls (P=.01). Elastin content of injured vessels was 2.40+/-0.43 mg/arterial segment compared to 1.19+/-0.25 mg/arterial segment in controls (P=.03).

CONCLUSIONS

Collagen and elastin contents were significantly increased following injury of the rat carotid. This study provides for the first time a biochemical assessment of collagen and elastin in the balloon-injured rat carotid artery.

Pathologic and histologic results of electrical impulses in a rabbit model of atherosclerosis: 24-hour versus 8-hour regimen

OBJECTIVE

Low frequency electrical impulses (EIs) reduce new atherosclerotic plaque formation in previously diseased arteries and may reverse the extent of previous pathologic damage in these structures.

METHODS

A pacemaker was implanted on the left side of rabbit abdominal aortas, and an electrode was placed close to the other side of the aorta in the psoas major muscle. For the induction of atherosclerosis, the rabbits were placed on a high cholesterol diet (HCD) for 11 weeks. No EIs were applied to the control series I. In the experimental series, the rabbits were fed an HCD for 3 weeks, after which EIs were applied simultaneously with an HCD for 8 additional weeks (3V, 30 contractions per minute). Experimental series II had 24-hour/day EIs, and series III had 8-hour/day EIs.

RESULTS

The closer to the area where the EIs were applied, the more local severity increased (atherosclerosis level and surface area). In the control series, the severity of atherosclerosis in the lower aorta assessed with an arbitrary grading system was 1.75 +/- 0.5 (versus 1.5 +/- 0.57 with 8-hour/day EIs and 0.5 +/- 0.3 with 24-hour/day EIs). The involved surface area was 32.5% +/- 9.5% (versus 1.0% +/- 0.8% with 8-hour/day EIs and 0.75% +/- 0.95% with 24-hour/day EIs).

CONCLUSION

Both 24-hour/day and 8-hour/day EIs applied close to the abdominal aorta decreased the severity of atherosclerosis in rabbits placed on a HCD, but 24-hour/day EIs decreased the severity more extensively.

Reduction in dermal fibrosis in the tight-skin (Tsk) mouse after local application of halofuginone

The effect of dermal application of halofuginone-an inhibitor of collagen type I synthesis-on skin collagen and collagen alpha1(I) gene expression in an animal model of scleroderma and chronic graft versus host disease (cGvHD) was evaluated. Halofuginone-containing cream was applied on the tight-skin mouse (Tsk) and skin biopsies were taken for collagen staining by sirius red and for collagen alpha1(I) gene expression by in situ hybridization. In addition, cell proliferation was evaluated by immunostaining for proliferation cell nuclear antigen (PCNA) alone or in combination with collagen alpha1(I) probe. The number of mast cells was assessed by toluidine blue. Dermal application of halofuginone (0.01%) for 60 days was as good as systemic administration (1 microg/mouse/day) in reducing collagen alpha1(I) gene expression in skin biopsy and almost as good in reducing skin width. Halofuginone was stable and effective only at acidic pH. The effect of halofuginone (0.03%) was time-dependent. After 40 days of daily treatment, a significant reduction in the collagen alpha1(I) gene expression was observed and further decrease was observed after 60 days. The reduction in collagen alpha1(I) gene expression and the reduction in the proliferation of dermal fibroblasts probably occur in the same subset of cells. No effect of halofuginone on the proliferation of keratinocytes or on mast cell number was observed. These results suggest that target-oriented application of halofuginone may become a novel therapy for fibrotic disorders in general and for scleroderma in particular.

Identification of new therapies for leiomyomas: what in vitro studies can tell us

Leiomyomas are a significant problem in women's health. An understanding of the biology of these tumors and how their growth is regulated is emerging from in vitro studies using tissue specimens and cultured cells. These studies have clarified how the ovarian steroid hormones regulate growth of uterine SMCs and how the ovarian steroid ligand-receptor system has been altered in leiomyomas. Such information will allow investigators to identify steroid hormone antagonists and steroid hormone receptor modulators that may be useful for treatment of leiomyomas. We are now also developing a much better understanding of the growth factors that are produced by SMCs of leiomyoma tumors. These growth factors not only regulate the proliferation, apoptosis, and extra-cellular matrix production of the SMCs but also regulate proliferation and migration of vascular endothelial cells. Targeting these growth factors and their receptors can reduce leiomyoma growth through two different mechanisms. One targets the SMCs and the other targets the vascular system that supports the growth of the tumor. Another important lesson that can be learned from reading the scientific literature is that there are striking similarities between the biology of uterine leiomyomas and other pathologic diseases that involve mesenchymally derived cells. These include benign keloids, other fibrotic diseases such as pulmonary fibrosis, and vascular diseases such as atherosclerosis. Compounds that are developed to treat these conditions may also be beneficial for treatment of uterine leiomyomas. The next few years will undoubtedly yield many new drug discoveries for these diseases.

Halofuginone: a potent inhibitor of critical steps in angiogenesis progression

We have previously demonstrated that halofuginone, a low molecular weight quinazolinone alkaloid, is a potent inhibitor of collagen alpha1(I) and matrix metalloproteinase 2 (MMP-2) gene expression. Halofuginone also effectively suppresses tumor progression and metastasis in mice. These results together with the well-documented role of extracellular matrix (ECM) components and matrix degrading enzymes in formation of new blood vessels led us to investigate the effect of halofuginone on the angiogenic process. In a variety of experimental system, representing sequential events in the angiogenic cascade, halofuginone treatment resulted in profound inhibitory effect. Among these are the abrogation of endothelial cell MMP-2 expression and basement membrane invasion, capillary tube formation, and vascular sprouting, as well as deposition of subendothelial ECM. The most conclusive anti-angiogenic activity of halofuginone was demonstrated in vivo (mouse corneal micropocket assay) by showing a marked inhibition of basic fibroblast growth factor (bFGF) -induced neovascularization in response to systemic administration of halofuginone, either i.p. or in the diet. The ability of halofuginone to interfere with key events in neovascularization, together with its oral bioavailability and safe use as an anti-parasitic agent, make it a promising drug for further evaluation in the treatment of a wide range of diseases associated with pathological angiogenesis.

Inhibitory mechanisms by which suramin may attenuate neointimal formation after balloon angioplasty

Restenotic neointimal lesions, a major limitation to coronary angioplasty, develop in response to diverse signals and depend on three properties of activated arterial smooth muscle cells (SMCs): proliferation, migration, and abnormal production of extracellular matrix. Most of the pharmacologic approaches targeting specific pathogenic factors facilitating development of restenosis have failed in clinical trials. Our results indicate that the polysulfonated naphthylurea suramin, a "non-specific drug" that interferes with multiple cellular proteins, inhibits neointimal formation in rabbit iliac arteries after balloon-catheter injury administered throughout the critical period of several weeks after the procedure. In vitro studies aimed at dissecting the mechanism(s) underlying the suramin-dependent effect demonstrated that, in addition to an inhibitory effect on SMC proliferation, suramin inhibited fibronectin and elastin deposition and the migration of SMCs through elastin membranes and into scratch gaps of monolayer cultures. We also demonstrated that suramin causes cell-surface accumulation of the elastin binding protein, a receptor that not only anchors SMCs to the extracellular matrix, but also inhibits SMC response to interleukin-1beta (IL-1beta). We conclude that suramin acts as a multitarget inhibitor of SMC activation and has a therapeutic potential as an agent that may attenuate arterial restenosis after angioplasty.

Prostacyclin synthase gene transfer accelerates reendothelialization and inhibits neointimal formation in rat carotid arteries after balloon injury

Prostacyclin (PGI2), a metabolite of arachidonic acid, has the vasoprotective effects of vasodilation, anti-platelet aggregation, and inhibition of smooth muscle cell proliferation. We hypothesized that an overexpression of endogenous PGI2 may accelerate the recovery from endothelial damage and inhibit neointimal formation in the injured artery. To test this hypothesis, we investigated in vivo transfer of the PGI2 synthase (PCS) gene into balloon-injured rat carotid arteries by a nonviral lipotransfection method. Seven days after transfection, a significant regeneration of endothelium was observed in the arteries transfected with a plasmid carrying the rat PCS gene (pCMV-PCS), but little regeneration was seen in those with the control plasmid carrying the lacZ gene (pCMV-lacZ) (percent luminal circumference lined by newly regenerated endothelium: 87. 1+/-6.9% in pCMV-PCS-transfected vessels and 6.9+/-0.2% in pCMV-lacZ vessels, P<0.001). BrdU staining of arterial segments demonstrated a significantly lower incorporation in pCMV-PCS-transfected vessels (7. 5+/-0.3% positive nuclei in vessel cells) than in pCMV-lacZ (50. 7+/-9.6%, P<0.01). Moreover, 2 weeks after transfection, the PCS gene transfer resulted in a significant inhibition of neointimal formation (88% reduction in ratio of intima/media areas), whereas medial area was similar among the groups. Arterial segments transfected with pCMV-PCS produced significantly higher levels of 6-keto-PGF1alpha, the main metabolite of PGI2, compared with the segments transfected with pCMV-lacZ (10.2+/-0.55 and 2.1+/-0.32 ng/mg tissue for pCMV-PCS and pCMV-placZ, P<0.001). In conclusion, this study demonstrated that an in vivo PCS gene transfer increased the production of PGI2 and markedly inhibited neointimal formation with accelerated reendothelialization in rat carotid arteries after balloon injury.

Evidence for a role of collagen synthesis in arterial smooth muscle cell migration

Migration of smooth muscle cells (SMCs) and collagen synthesis by SMCs are central to the pathophysiology of vascular disease. Both processes can be induced shortly after vascular injury; however, a functional relationship between them has not been established. In this study, we determined if collagen synthesis was required for SMC migration, using ethyl-3,4-dihydroxybenzoate (EDHB), an inhibitor of prolyl-4-hydroxylase, and 3,4-DL-dehydroproline (DHP), a proline analogue, which we demonstrate inhibit collagen elaboration by porcine arterial SMCs. SMCs exposed to EDHB or DHP attached normally to collagen- and vitronectin-coated substrates; however, spreading on collagen but not vitronectin was inhibited. SMC migration speed, quantified by digital time-lapse video microscopy, was significantly and reversibly reduced by EDHB and DHP. Flow cytometry revealed that expression of beta1 integrins, through which SMCs interact with collagen, was unaffected by EDHB or DHP. However, both inhibitors prevented normal clustering of beta1 integrins on the surface of SMCs, consistent with a lack of appropriate matrix ligands for integrin engagement. Moreover, there was impaired recruitment of vinculin into focal adhesion complexes of spreading SMCs and disassembly of the smooth muscle alpha-actin-containing cytoskeleton. These findings suggest that de novo collagen synthesis plays a role in SMC migration and implicates a mechanism whereby newly synthesized collagen may be necessary to maintain the transcellular traction system required for effective locomotion.

Halofuginone: a novel antifibrotic therapy

1. Fibrosis is characterized by extracellular matrix deposition, of which collagen type I is the major constituent. The progressive accumulation of connective tissue resulted in destruction of normal tissue architecture and function. 2. Fibrosis is a common response to various insults or injuries and can be the outcome of any perturbation in the cellular function of any tissue. 3. Halofuginone was found to inhibit collagen alpha 1(I) gene expression and collagen synthesis in a variety of cell cultures including human fibroblasts derived from patients with excessive skin collagen type I synthesis. 4. Halofuginone was found to inhibit collagen alpha 1(I) gene expression and collagen synthesis in animal models characterized by excessive deposition of collagen. In these models, fibrosis was induced in various tissues such as skin, liver, lung, etc. Halofuginone was injected intraperitoneally, added to the foodstuff or applied locally. 5. Halofuginone decreased skin collagen in a chronic graft-versus-host disease patient. 6. The ability of extremely low concentrations of halofuginone to inhibit collagen alpha 1(I) synthesis specifically and transiently at the transcriptional level suggests that this material fulfills the criteria for a successful and effective anti-fibrotic therapy.

Halofuginone inhibits neointimal formation of cultured rat aorta in a concentration-dependent fashion in vitro

Halofuginone, an anticoccidial quinoazolinone, can specifically inhibit collagen type alpha1 (I) synthesis and gene expression, and also inhibits cultured smooth muscle cell proliferation. The aim of this study was to investigate the effect of halofuginone on neointimal formation of rat aorta after culture in a concentration-dependent manner in vitro. Thoracic aorta of Wistar rats was removed and manipulated to damage the endothelium under sterile conditions, and culture for 15 days in halofuginone-free or halofuginone-added culture medium (n = 20). Segments of cultured aorta were studied by histologic and immunohistochemical methods. Proliferation of neointimal layers consisting of loose multilayer cellular structure was observed in the halofuginone-free control group after 15 days of rat aorta culture, and neointimal formation was significantly decreased as an increasing concentration of halofuginone was added. As with precultured fresh aorta, no intimal proliferation was observed in the cultured segments of aorta with 500 ng/ml halofuginone added to culture medium. The proliferation of cell nuclear antigen index was significantly higher in the halofuginone-free control group than that in the halofuginone-added groups. The present results suggest that halofuginone can inhibit neointimal formation of rat aorta after culture in a concentration-dependent fashion in vitro.

Inhibition of glomerular mesangial cell proliferation and extracellular matrix deposition by halofuginone

Mesangial cell proliferation, increased deposition of collagen, and expansion of the mesangial extracellular matrix (ECM) are key features in the development of mesangioproliferative diseases. Halofuginone, a low molecular weight anti-coccidial quinoazolinone derivative, inhibits collagen type alpha 1(I) gene expression and synthesis. We investigated the effect of halofuginone on both normal and SV40 transformed mesangial cell proliferation, collagen synthesis, and ECM deposition. Proliferation of both cell types was almost completely inhibited in the presence of 50 ng/ml halofuginone. The cells were arrested in the late G1 phase of the cell cycle and resumed their normal growth rate following removal of the compound from the culture medium. The antiproliferative effect of halofuginone was associated with inhibition of tyrosine phosphorylation of cellular proteins. Similar results were obtained whether the mesangial cells were seeded on regular tissue culture plastic or in close contact with a naturally produced ECM resembling their local environment in vivo. Halofuginone also inhibited synthesis and deposition of ECM by mesangial cells as indicated by a substantial reduction in 14C-glycine and Na2(35)SO4 incorporation into the ECM, and by the inhibition of collagen type I synthesis and gene expression. It is proposed that by inhibiting collagen type I synthesis and matrix deposition, halofuginone exerts a potent antiproliferative effect that may be applied to inhibit mesangial cell proliferation and matrix expansion in a variety of chronic progressive glomerular diseases.

Halofuginone, a specific inhibitor of collagen type I synthesis, prevents dimethylnitrosamine-induced liver cirrhosis

BACKGROUND/AIMS

Hepatic cirrhosis is characterized by excessive deposition of collagen, resulting from an increase in type I collagen gene transcription. We evaluated the effect of halofuginone-a specific inhibitor of collagen type alpha 1(I) gene expression-on dimethylnitrosamine (DMN)-induced liver fibrosis/cirrhosis in rats.

METHODS

Fibrosis was induced by intraperitoneal injection of DMN. Halofuginone (5 mg/kg) was added to the diet. Collagen was stained with Sirius red and collagen alpha 1(I) gene expression was evaluated by in situ hybridization.

RESULTS

In control rats, a low level of collagen alpha 1(I) gene expression was observed. A high dose of DMN (1%) caused severe fibrosis, as indicated by induction of collagen alpha 1(I) gene expression and increased liver collagen content. Addition of halofuginone before the onset of fibrosis, almost completely prevented the increase in collagen type I gene expression and resulted in lower liver collagen content. Moreover, halofuginone partially prevented the marked decrease in liver weight and reduced the mortality rate. At a lower dose of DMN (0.25%), which causes mild fibrosis, halofuginone prevented the increase in collagen alpha 1(I) gene expression, prevented the increase in liver collagen deposition and reduced plasma alkaline phosphatase activity, all of which are characteristic of liver fibrosis/ cirrhosis.

CONCLUSIONS

These results suggest that halofuginone can be used as an important tool to understand the regulation of the collagen alpha 1(I) gene and may become a novel and promising antifibrotic agent for liver fibrosis/ cirrhosis.