Endogenous nitric oxide synthase inhibitors in endothelial cells, endothelin-1 within the vessel wall, and intimal hyperplasia in perimenopausal human uterine arteries

Efficacy, safety and mechanism of Honghua Xiaoyao Pill in the treatment of peri-menopausal syndrome: A study protocol for a randomized controlled trial

Background: Peri-menopausal syndrome (PMPS) has a high incidence rate and seriously affects the physical and mental health of women. Honghua Xiaoyao Pill (HHXYP) is a Chinese patent medicine, which has been reported to be used to treat PMPS. However, there is still a lack of randomized clinical trial to evaluate the efficacy and safety of HHXYP on life quality, mood and vasomotor symptoms for PMPS women. This study aims to investigate whether HHXYP is effective and safe in treating PMPS and the possible mechanism. Methods: A multicenter, randomized, controlled clinical trial will be conducted in China to evaluate the efficacy and safety of HHXYP. Sixty women with peri-menopausal syndrome will be recruited at three centers and randomly in a 1:1 ratio to a treatment group using HHXYP (HHXYP group) and a control group using oryzanol (OC group). Participants will be treated with HHXYP or oryzanol for 12 weeks and followed up for 4 weeks. The primary outcome is the modified Kupperman Index (KI), which will be measured at baseline and 4, 8, 12, 16 weeks after randomization. The secondary outcomes include Hot flash scale (HFs), Menopause-Specific Quality of Life Scale (MENQOL) and Hamilton Depression/Anxiety Scale (HAMD/HAMA). The HFs are measured at the same point as the KI, other secondary outcomes are measured at baseline and 12, 16 weeks after randomization. The other outcomes are the levels of serum sex hormone, monoamine neurotransmitter, vascular vasomotor factor and the expression of phosphatidylinositol 3-active enzyme (PI3K)/protein activator enzyme B (Akt), which will be measured at baseline and 12 weeks after randomization. Adverse events will also be reported. Discussion: HHXYP is a potential alternative Chinese patent medicine for PMPS. This trial will provide evidence for HHXYP on improving the quality of life, mood and vasomotor symptoms, and sex hormone levels of PMPS patients.

ADMA: its role in vascular disease

Endothelium-derived nitric oxide (NO) is the most potent endogenous vasodilator and, by virtue of its anti-inflammatory and anti-thrombotic effects, it is an endogenous anti-atherogenic agent. Accordingly, impairment of NO synthesis or bioactivity may increase the risk of vascular disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of the NO synthase pathway. Plasma levels of ADMA are increased in patients with vascular disease, or with risk factors for vascu lar disease. Preclinical and clinical studies indicate that ADMA may mediate the adverse effects of traditional risk factors on endothelial vasodilator function. By impairing endothelial function, ADMA may contribute to pulmonary or systemic hypertension, as well as to vascular disease. Several drugs known to treat cardiovas cular disease also reduce plasma ADMA levels, such as angiotensin receptor antag onists, converting enzyme inhibitors, and insulin sensitizing agents. Plasma ADMA may be a common mediator of endothelial dysfunction induced by vascular risk factors. Insights into the mechanisms by which plasma ADMA is regulated may lead to new therapeutic knowledge.

ADMA: its role in vascular disease

Endothelium-derived nitric oxide (NO) is the most potent endogenous vasodilator and, by virtue of its anti-inflammatory and anti-thrombotic effects, it is an endogenous anti-atherogenic agent. Accordingly, impairment of NO synthesis or bioactivity may increase the risk of vascular disease. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of the NO synthase pathway. Plasma levels of ADMA are increased in patients with vascular disease, or with risk factors for vascular disease. Preclinical and clinical studies indicate that ADMA may mediate the adverse effects of traditional risk factors on endothelial vasodilator function. By impairing endothelial function, ADMA may contribute to pulmonary or systemic hypertension, as well as to vascular disease. Several drugs known to treat cardiovascular disease also reduce plasma ADMA levels, such as angiotensin receptor antagonists, converting enzyme inhibitors, and insulin sensitizing agents. Plasma ADMA may be a common mediator of endothelial dysfunction induced by vascular risk factors. Insights into the mechanisms by which plasma ADMA is regulated may lead to new therapeutic knowledge.

Stimulated angiogenesis for fracture healing augmented by low-magnitude, high-frequency vibration in a rat model-evaluation of pulsed-wave doppler, 3-D power Doppler ultrasonography and micro-CT microangiography

This study aimed to investigate the mechanism of low-magnitude high-frequency vibration (LMHFV) treatment on angiogenesis and blood flow for enhancement of fracture healing. Nine-month-old ovariectomized (OVX) and sham-operated (Sham) rats received closed fractures creation at the femora and were randomized into LMHFV treatment (Sham-V, OVX-V) or control (Sham-C, OVX-C) groups. Pulsed-wave Doppler indicated an increase in blood flow velocity of the femoral artery at weeks 2 (OVX pair: p = 0.030) and 4 (OVX pair: p = 0.012; Sham pair: p = 0.020) post-treatment. Significantly enhanced vascular volume (VV) at the fracture site in the vibration groups was demonstrated by 3-D high-frequency power Doppler at week 2 (Sham pair: p = 0.021) and micro-computed tomography (microCT) microangiography at weeks 2 (OVX pair: p = 0.009) and 4 (OVX pair: p = 0.034), which echoed the osteogenesis findings by radiographic and microCT analysis. VV in the OVX groups was inferior to the Sham groups. However, OVX-V showed higher percentages of angiogenic enhancement than Sham-V. Despite impaired neo-angiogenesis in osteoporotic fractures, LMHFV could increase blood flow and angiogenesis in both normal and osteoporotic fractures, thus enhancing fracture healing.

Cell-permeant peptide inhibitors of vasospasm and intimal hyperplasia

Outcomes from vein graft bypass are limited by graft failure, leading causes of which include intimal hyperplasia and vasospasm. Intimal hyperplasia remains the most common cause of graft failure, but no therapeutic modalities have been shown to prevent intimal hyperplasia in humans. The small heat shock proteins are a class of naturally occurring proteins in vascular smooth muscle. These proteins have an integral role in maintenance of vascular tone and in cellular defense against various stressors. Transduction domains have enabled intracellular therapeutic delivery of peptide analogs of heat shock proteins, as well as peptide inhibitors of the kinases that phosphorylate these proteins. These cell-permeant peptides have been shown to prevent vasospasm and intimal hyperplasia in vitro. Since vascular bypass using vein grafts is analogous to autologous organ transplantation, ex vivo treatment of the vein graft with cell-permeant peptide inhibitors of vasospasm and intimal hyperplasia prior to implantation provides a unique opportunity for targeted treatment of the graft to improve patency.

Intimal hyperplasia: slow but deadly

Intimal hyperplasia is the leading cause of long-term failure in coronary artery bypass vein grafting, coronary artery stenting, angioplasty, arteriovenous fistula for dialysis, and allograft transplantation. Intimal hyperplasia is a product of vascular smooth muscle cell proliferation, migration through the internal elastic lamina, and deposition of extracellular matrix proteins driven by growth factors in the vasculature. This vascular pathology results in a progressive diminution of the vessel lumen and serves as a site for thrombosis and atherosclerotic lesions. A key cell type in the initiation of intimal hyperplasia is the vascular endothelial cell, which appears to have down-stream effects on the vascular smooth muscle proliferation and migration. Currently, the only means available for prevention of intimal hyperplasia is through inhibition of mammalian target of rapamycin (mTOR) with the immunosuppressant rapamycin. mTOR integrates up-stream signals from growth factors such as IL-2 and senses the cellular nutrient and energy levels and redox status. This presentation will discuss the potential means of preserving the vascular endothelial cell and, thereby, reducing the development of intimal hyperplasia in our open-heart surgical patients.

Non-endothelial endothelin counteracts hypoxic vasodilation in porcine large coronary arteries

Background

The systemic vascular response to hypoxia is vasodilation. However, reports suggest that the potent vasoconstrictor endothelin-1 (ET-1) is released from the vasculature during hypoxia. ET-1 is reported to augment superoxide anion generation and may counteract nitric oxide (NO) vasodilation. Moreover, ET-1 was proposed to contribute to increased vascular resistance in heart failure by increasing the production of asymmetric dimethylarginine (ADMA). We investigated the role of ET-1, the NO pathway, the potassium channels and radical oxygen species in hypoxia-induced vasodilation of large coronary arteries.

Results

In prostaglandin F_2α (PGF_2α, 10 μM)-contracted segments with endothelium, gradual lowering of oxygen tension from 95 to 1% O₂ resulted in vasodilation. The vasodilation to O₂ lowering was rightward shifted in segments without endothelium at all O₂ concentrations except at 1% O₂. The endothelin receptor antagonist SB217242 (10 μM) markedly increased hypoxic dilation despite the free tissue ET-1 concentration in the arterial wall was unchanged in 1% O₂ versus 95% O_2. Exogenous ET-1 reversed hypoxic dilation in segments with and without endothelium, and the hypoxic arteries showed an increased sensitivity towards ET-1 compared to the normoxic controls. Without affecting basal NO, hypoxia increased NO concentration in PGF_2α-contracted arteries, and an NO synthase inhibitor, L-NOARG,(300 μM, N^G-nitro-L-Arginine) reduced hypoxic vasodilation. NO-induced vasodilation was reduced in endothelin-contracted preparations. Arterial wall ADMA concentrations were unchanged by hypoxia. Blocking of potassium channels with TEA (tetraethylammounium chloride)(10 μM) inhibited vasodilation to O₂ lowering as well as to NO. The superoxide scavenger tiron (10 μM) and the putative NADPH oxidase inhibitor apocynin (10 μM) leftward shifted concentration-response curves for O₂ lowering without changing vasodilation to 1% O₂. PEG (polyethylene glycol) catalase (300 u/ml) inhibited H₂O₂ vasodilation, but failed to affect vasodilation to O₂ lowering. Neither did PEG-SOD (polyethylene glycol superoxide dismutase)(70 u/ml) affect vasodilation to O₂ lowering. The mitochondrial inhibitors rotenone (1 μM) and antimycin A (1 μM) both inhibited hypoxic vasodilatation.

Conclusion

The present results in porcine coronary arteries suggest NO contributes to hypoxic vasodilation, probably through K channel opening, which is reversed by addition of ET-1 and enhanced by endothelin receptor antagonism. These latter findings suggest that endothelin receptor activation counteracts hypoxic vasodilation.

Regulation of myometrial contractivity during pregnancy in the rat: potential role for DDAH

There has been little information demonstrating the roles of dimethylarginine dimethylaminohydrolase (DDAH), which is the hydrolyzing enzyme of endogenous nitric oxide synthase (NOS) inhibitors and, in turn, modulates the intracellular concentrations of NOS inhibitors, in the myometrium during the course of pregnancy. Therefore, the present experiments were designed to investigate whether or not DDAH activity, protein and mRNA expression levels are altered during gestation of the rat and, if altered, those changes reflect on the levels of endogenous inhibitors and endothelin-1 (ET-1), and NO-dependent cyclic GMP generation in the myometrium. The up-regulated changes in DDAH activity, DDAH-2 protein and DDAH-2 mRNA expression at mid-gestation were accompanied by the reduced monomethylarginine and asymmetric dimethylarginine as NOS inhibitors, and ET-1 levels, and by the enhanced NO-dependent cyclic GMP production. At term gestation, on the other hand, down-regulated changes in DDAH activity, DDAH-2 protein and DDAH-2 mRNA expression were accompanied by the increased NOS inhibitors and ET-1 levels, and decreased NO-dependent cyclic GMP generation. These results suggest that alterations in DDAH/NOS inhibitors/NO-dependent cyclic GMP/ET-1 pathway are possibly involved in maintaining myometrial quiescence during gestation and controlling delivery at term.

Possible involvement of altered arginase activity, arginase type I and type II expressions, and nitric oxide production in occurrence of intimal hyperplasia in premenopausal human uterine arteries

In the present experiments, we tried to elucidate whether changes in arginase activity and protein expression of arginase I and II are involved in the occurrence of intimal hyperplasia in premenopausal human uterine arteries. They were obtained from thirty-four patients undergoing total abdominal hysterectomy with informed consent for the present study. All specimens were assessed histologically and the intima/media ratio (%) was evaluated as an index of the intimal hyperplasia. Thirteen patients out of 34 had histologically normal arteries (intima/media ratio = 18.1 +/- 0.7%), whereas the remaining 21 patients had various degrees of intimal hyperplasia (intima/media ratio = 32.7 +/- 2.3%), and these specimens were categorized as hyperplasic. Intimal hyperplasia was accompanied by impaired cyclic GMP production, enhanced overall arginase activity, and up-regulations of arginase I and II in endothelial cells and of arginase II in the smooth muscle layer. Pearson's correlation coefficient analyses revealed the close relationships among the arginase activities in endothelial cells and smooth muscle layer, the intimal/media ratio, and cyclic GMP production. These results suggest that the enhanced arginase activity and expressions of two arginase subtypes shed new light on the processes associated with the occurrence of intimal hyperplasia in premenopausal human uterine arteries.

Involvement of accumulated NOS inhibitors and endothelin-1, enhanced arginase, and impaired DDAH activities in pulmonary dysfunction following subarachnoid hemorrhage in the rabbit

We designed the present experiments to investigate the involvement of endogenous nitric oxide synthase (NOS) inhibitors, dimethylarginine dimethylaminohydrolase (DDAH) as a hydrolyzing enzyme of the NOS inhibitors, NOS, arginase which shares l-arginine as a common substrate with NOS, and endothelin-1 (ET-1) in the pulmonary dysfunction after induction of experimental subarachnoid hemorrhage (SAH) in the rabbit. SAH was induced by injecting autologous blood into the cisterna magna, and controls were injected with saline. On day 2, pulmonary arteries were isolated for determinations. A significant impairment of the endothelium-dependent relaxation (EDR) caused by acetylcholine was found in 20 cases (43.5%) out of 46 SAH animals, and the same animals exhibited accompanying the significantly impaired cyclic GMP production, accumulated endogenous NOS inhibitors, attenuated DDAH activity, enhanced arginase activity and accumulated ET-1 within the vessel wall. Meanwhile, there were no differences in endothelial NOS activity per se and sodium nitroprusside-induced relaxation between the animals with an impaired EDR and those without such a change. ET-1 content within aortic wall was increased with concomitant decrease in cyclic GMP production after the intraperitoneal application of authentic monomethylarginine as a NOS inhibitor in the rat. The current results suggest that accumulated endogenous NOS inhibitors and enhanced arginase activity possibly bring about the impaired NO production, thereby attenuating the EDR and contributing to the accumulation of ET-1 within the vessel wall. The accumulated endogenous NOS inhibitors at least partly result from the decreased DDAH activity. These alterations may be relevant to the pulmonary dysfunction after induction of SAH.

Alterations of NOS, arginase, and DDAH protein expression in rabbit cavernous tissue after administration of cigarette smoke extract

Cigarette smoking is an independent risk factor for vasculogenic erectile dysfunction (ED). Nitric oxide (NO) has been demonstrated to be the principal mediator of cavernous smooth muscle relaxation and penile erection. Therefore, we examined whether or not enzyme activities and factors involved in the NO generation pathway are affected in rabbit corpus cavernosum after administration of nicotine- and tar-free cigarette smoke extract (CSE). CSE was prepared by bubbling a stream of cigarette smoke into phosphate-buffered saline. CSE was injected subcutaneously into adult male rabbits once a day for 5 wk. In the CSE group, significantly decreased cyclic GMP production as a marker of NO generation was associated with attenuated overall nitric oxide synthase (NOS) activity, enhanced arginase activity, accumulation of endogenous NOS inhibitors such as monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), and decreased dimethylarginine dimethylaminohydrolase (DDAH) activity as an metabolizing enzyme of endogenous NOS inhibitors. Neuronal NOS (nNOS) and DDAH I protein expression were decreased without altering endothelial NOS expression, while arginase I expression was upregulated. These results suggest that impaired NO production would result from blunted NOS activity, which is possibly brought about by the downregulation of nNOS protein, accumulation of endogenous NOS inhibitors, and enhanced arginase activity together with upregulation of arginase I protein in cavernous tissue. The impaired DDAH activity due to decreased expression of DDAH I protein would result in an accumulation of endogenous NOS inhibitors with CSE. These alterations may be relevant to induction of the erectile dysfunction following CSE.

Analysis of arterial intimal hyperplasia: review and hypothesis

BACKGROUND

Despite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology?

HYPOTHESIS

I argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign" intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates early in life to form a multi-layer intimal hyperplasia and then continues to self-renew in a controlled manner throughout life, relatively rarely compromising the blood supply to the heart, causing complications requiring intervention only in a small fraction of the population, while all humans are carriers of benign hyperplasia. Unfortunately, this fundamental fact has not been widely appreciated in arteriosclerosis research and medical education, which continue to operate on the assumption that the normal arterial intima is always an "ideal" single-layer endothelium. As a result, the disease is perceived and studied as a new pathological event caused by new mechanisms. The discovery that normal coronary arteries are morphologically indistinguishable from deadly coronary arteriosclerosis continues to elicit surprise.

CONCLUSION

Two questions should inform the priorities of our research: (1) what controls switch the single cell-layer intimal phenotype into normal hyperplasia? (2) how is normal (benign) hyperplasia maintained? We would be hard-pressed to gain practical insights without scrutinizing our premises.

Possible involvement of enhanced arginase activity due to up-regulated arginases and decreased hydroxyarginine in accelerating intimal hyperplasia with hyperglycemia

The present study was designed to investigate the roles of enhanced arginase activity due to up-regulated arginases and the decreased hydroxyarginine for accelerating intimal hyperplasia with hyperglycemia. Thirteen weeks after injection of alloxan or physiological saline, endothelial denudation of the carotid artery was performed to induce intimal hyperplasia. The intimal hyperplasia occurred on 4 weeks following denudation was significantly accelerated by hyperglycemia. The method to measure L-arginine, endogenous NOS inhibitors such as monomethylarginine and asymmetric dimethylarginine, and hydroxyarginine as an intermediate of NO production simultaneously was established with the aid of high-performance liquid chromatography. In hyperglycemia group, the impaired cyclic GMP production as an indicator of NO production in endothelial cells was accompanied by the enhanced arginase activity together with increased expression of arginase I and II proteins, accumulated endogenous NOS inhibitors, reduced concentration of hydroxyarginine, and decreased DDAH activity in endothelial cells. However, NOS activity per se remained unchanged in the hyperglycemia group. Authentic hydroxyarginine inhibited arginase activity in a concentration-dependent manner. The inhibition of arginase with hydroxyarginine at a reduced concentration with hyperglycemia became significantly lower than that for the control. These results suggest that the accelerated intimal hyperplasia with hyperglycemia is closely related to the impaired NO production in endothelial cells, which results from accumulation of endogenous NOS inhibitors and accelerated arginase activity together with up-regulation of arginase I and II proteins. Decreased DDAH activity would bring about the accumulation of endogenous NOS inhibitors. Furthermore, reduced concentration of hydroxyarginine with hyperglycemia possibly results in an enhanced arginase activity in vivo, implicating partly in the impairment of NO production.

HPLC analysis of ADMA and other methylated l-arginine analogs in biological fluids

Post-translational methylation of arginine residues in proteins leads to generation of N(G)-monomethylarginine (MMA) and both symmetric and asymmetric dimethylarginine (SDMA and ADMA), that are released into the cytosol upon proteolysis. Both MMA and ADMA are inhibitors of nitric oxide synthase and especially elevated levels of ADMA are associated with endothelial dysfunction and cardiovascular disease. Plasma concentrations of ADMA and SDMA are very low, typically between 0.3 and 0.8 microM, making their quantification by HPLC an analytical challenge. Sample preparation usually involves a cleanup step by solid-phase extraction on cation-exchange columns followed by derivatization of amino acids into fluorescent adducts. Because ADMA and SDMA concentrations in healthy subjects show a very narrow distribution, with a between-subject variability of 13% for ADMA and 19% for SDMA, very low imprecision is an essential assay feature. Procedures for sample cleanup, derivatization, and chromatographic separation of arginine and its methylated analogs are the main topics of this review. In addition, important aspects of method validation, pre-analytical factors, and reference values are discussed.

Roles of accumulated endogenous nitric oxide synthase inhibitors, enhanced arginase activity, and attenuated nitric oxide synthase activity in endothelial cells for pulmonary hypertension in rats

Nitric oxide (NO) has been suggested to play a key role in the pathogenesis of pulmonary hypertension (PH). To determine which mechanism exists to affect NO production, we examined the concentration of endogenous nitric oxide synthase (NOS) inhibitors and their catabolizing enzyme dimethylarginine dimethylaminohydrolase (DDAH) activity and protein expression (DDAH1 and DDAH2) in pulmonary artery endothelial cells (PAECs) of rats given monocrotaline (MCT). We also measured NOS and arginase activities and NOS protein expression. Twenty-four days after MCT administration, PH and right ventricle (RV) hypertrophy were established. Endothelium-dependent, but not endothelium-independent, relaxation and cGMP production were significantly impaired in pulmonary artery specimens of MCT group. The constitutive NOS activity and protein expression in PAECs were significantly reduced in MCT group, whereas the arginase, which shares l-arginine as a common substrate with NOS, activity was significantly enhanced in PAECs of MCT group. The contents of monomethylarginine (MMA) and asymmetric dimethylarginine (ADMA), but not symmetric dimethylarginine (SDMA), were increased in PAECs of MCT group. The DDAH activity and DDAH1, but not DDAH2, protein expression were significantly reduced in PAECs of MCT group. These results suggest that the impairment of cGMP production as a marker of NO production is possibly due to the blunted endothelial NOS activity resulting from the downregulation of endothelial NOS protein, accumulation of endogenous NOS inhibitors, and accelerated arginase activity in PAECs of PH rats. The decreased overall DDAH activity accompanied by the downregulation of DDAH1 would bring about the accumulation of endogenous NOS inhibitors.

Estrogen replacement effectively improves the accelerated intimal hyperplasia following balloon injury of carotid artery in the ovariectomized rats

Present experiments were designed to investigate the effects of ovariectomy (OVX) and estrogen replacement (ER) on neointimal formation after balloon injury of the rat carotid artery. Young adult female rats were divided into 3 groups of sham operation (control), ovariectomy, and ovariectomy plus estrogen replacement. Estrogen replacement was initiated by implanting a sustained release pellet containing water-soluble 17beta-estradiol 1 week after the ovariectomy. Carotid arteries were harvested 2 weeks after the balloon injury for determinations. The balloon injury caused intimal hyperplasia, which was accompanied by the impaired endothelium-dependent relaxation and cyclic GMP production, and accumulation of asymmetric dimethylarginine (ADMA) as an endogenous NOS inhibitor. Bilateral ovariectomy accelerated the intimal hyperplasia. The acceleration was accompanied by the enhanced impairment of NO production, attenuated reendothelialization, and enhanced accumulation of ADMA. The estrogen replacement improved the accelerated intimal hyperplasia with concomitant improvement of the impaired NO production and accumulated asymmetric dimethylarginine, and facilitated reendothelialization. These results suggests that the enhanced impairment of NO production, which possibly results from the accumulated asymmetric dimethylarginine and lack of reendothelialization, may contribute to the acceleration of intimal hyperplasia by ovariectomy and that estrogen replacement effectively improves the intimal hyperplasia by restoring the impaired NO production through reducing endogenous NOS inhibitor and facilitating reendothelialization.

Accumulated endogenous nitric oxide synthase inhibitors, enhanced arginase activity, attenuated dimethylarginine dimethylaminohydrolase activity and intimal hyperplasia in premenopausal human uterine arteries

The present study was designed to investigate the involvement of nitric oxide synthase (NOS), endogenous NOS inhibitors, arginase, which shares L-arginine as a common substrate with NOS, and dimethylarginine dimethylaminohydrolase (DDAH) as a metabolizing enzyme of NOS inhibitors in the occurrence of intimal hyperplasia in premenopausal human uterine arteries. Fifty-two uterine arteries were obtained from 52 patients undergoing total hysterectomy with an informed consent for the present study. All specimens were assessed histologically and the intima:media ratio (%) was evaluated as an index of intimal hyperplasia. Nineteen specimens were found to be histologically normal (intima:media ratio=16.1+/-0.8%), whereas remaining 33 specimens were categorized as intimal hyperplasia (intima:media ratio=34.4+/-1.5%). The intimal hyperplasia was associated with the impaired cyclic GMP production without change in endothelial NOS activity per se, accumulation of endogenous NOS inhibitors in endothelial cells, attenuated DDAH activity in endothelial cells and enhanced arginase activity in endothelial cells and smooth muscle layer. These findings suggest that the impaired cyclic GMP production as a marker of NO production is possibly due to the accumulated endogenous NOS inhibitors and enhanced arginase activity, which, in turn, closely relates to the occurrence of intimal hyperplasia, and that the impaired DDAH activity would result in the accumulation of endogenous NOS inhibitors in endothelial cells. Because of the enhanced arginase activity in endothelial cells and smooth muscle layer, the accelerated polyamine biosynthetic pathway may be implicated in the occurrence of intimal hyperplasia in premenopausal human uterine arteries.

Transduction of peptide analogs of the small heat shock-related protein HSP20 inhibits intimal hyperplasia

BACKGROUND

Human saphenous vein (HSV) is the autologous conduit of choice for peripheral vascular reconstructions. However, vasospasm can lead to early graft failure. The leading cause of delayed graft failure is intimal hyperplasia.

OBJECTIVE

To develop a proteomic approach to prevent vein-graft spasm and intimal hyperplasia.

METHODS

Biomimetic peptide analogs of the small heat shock-related protein HSP20, containing a protein transduction domain (PTD), a phosphorylated serine, and a sequence of HSP20 surrounding the phosphorylation site (PTD-pHSP20), or a scrambled sequence of the same amino acids surrounding the phosphorylation site (PTD-scHSP20) were synthesized. The peptides were used in muscle bath and organ culture experiments with human saphenous vein (HSV) segments. Cultured smooth muscle cell lines were used to determine the effect of the peptides on proliferation and migration.

RESULTS

In HSV rings precontracted with norepinephrine, PTD-pHSP20 but not PTD-scHSP20 led to relaxation. There was no significant difference in smooth muscle cell proliferation in cells treated with PTD-pHSP20 compared with PTD-scHSP20. Treatment with PTD-pHSP20 significantly inhibited cellular migration compared with PTD-scHSP20. Control, untreated, and PTD-scHSP20-treated saphenous veins had significant increases in intimal thickness after culture. This intimal thickening was completely inhibited by treatment with PTD-pHSP20.

CONCLUSIONS

Protein transduction of biologically active motifs of HSP20 can affect pathologic and physiologic responses of HSV and represents a novel proteomic-based therapeutic approach.

CLINICAL RELEVANCE

We have been a part of the genomics era and are now viewing the emergence of "proteomics." The genome is linear and relatively easy to examine; however the proteome is much more complex and dynamic. In essence, the purpose of gene therapy is to manipulate the genome to produce a particular protein. This manuscript describes a new proteomic approach in which the biologically active part of a protein is directly introduced into vascular cells. Peptides were synthesized which contained a total of 24 amino acids, 11 of which represent a protein transduction domain or "carrier" while the other 13 are the biologically active "cargo." These synthetic peptides prevent spasm (contraction) and intimal hyperplasia in segments of human saphenous vein treated ex vivo. Preclinical development is currently underway to develop these molecules as a proteomic-based vein harvest solution to enhance vein-graft patency.

Possible involvement of facilitated polyol pathway in augmentation of intimal hyperplasia in rabbits with alloxan-induced hyperglycemia

Present experiments were designed to investigate whether the facilitated polyol pathway is involved in the augmentation of intimal hyperplasia with hyperglycemia. Twelve weeks after a single bolus intravenous injection of alloxan (100 mg/kg) or saline, rabbits underwent a unilateral endothelial denudation of the carotid artery. Intimal hyperplasia was evident 4 weeks after denudation and significantly augmented in hyperglycemic animals treated with alloxan. This effect was accompanied by the enhanced accumulation of endogenous NOS inhibitors (N(G)-monomethyl-l-arginine [l-NMMA] and asymmetric, N(G),N(G)-dimethyl-l-arginine [ADMA]) in regenerated endothelial cells, impairment of NO production and release, and enhanced accumulation of endothelin-1 (ET-1) within the vessel wall. Sorbitol levels in aortic endothelial cells and within the smooth muscle layer were significantly increased with hyperglycemia. All these changes associated with hyperglycemia were significantly reduced in animals treated with the selective aldose reductase inhibitor fidarestat (3 mg/kg/d). These findings suggest that the facilitated polyol pathway possibly plays an important role for the augmentation of intimal hyperplasia caused by the hyperglycemic state.

Acute intravenous L-arginine infusion decreases endothelin-1 levels and improves endothelial function in patients with angina pectoris and normal coronary arteriograms: correlation with asymmetric dimethylarginine levels

BACKGROUND

We tested the hypothesis that asymmetric dimethylarginine (ADMA) levels could be elevated and influence endothelin-1 and nitric oxide release and action in patients with cardiac syndrome X (CSX). In addition, we evaluated whether an intravenous infusion of L-arginine would improve endothelial function in these subjects.

METHODS AND RESULTS

Nine patients with CSX and 14 control subjects underwent a continuous infusion of L-arginine (0.125 g/min) or saline for 120 minutes. Sixty minutes after L-arginine or saline infusions, an intravenous insulin bolus (0.1 U/kg) combined with a euglycemic clamp was performed. Basal ADMA and endothelin-1 levels were higher in patients with CSX than in controls. At the end of the first hour of infusion, compared with saline, L-arginine infusion increased basal forearm blood flow, nitrite and nitrate (NOx), and forearm cGMP release and decreased endothelin-1. After insulin bolus, during saline, insulin-induced NOx, endothelin-1, and forearm cGMP release was almost abolished. Conversely, L-arginine restored a physiological profile of all endothelial variables compared with control subjects. In control subjects, compared with saline infusion, L-arginine infusion did not modify any parameter. ADMA levels were positively correlated with basal endothelin-1 levels and negatively correlated with insulin-induced incremental levels of NOx and forearm cGMP release.

CONCLUSIONS

Plasma ADMA levels are increased in patients with CSX, and they are correlated with increases in endothelin-1 and reductions in insulin-induced increments in plasma NOx and cGMP, effects that are reversed by intravenous L-arginine. These data suggest that increased ADMA levels play a role in the abnormal vascular reactivity that is observed in patients with CSX.