Protein tyrosine kinase inhibitors inhibit chemotaxis of vascular smooth muscle cells

Dietary Soy Isoflavone: A Mechanistic Insight

Soy, a major component of the diet for centuries contains the largest concentration of isoflavones, a class of phytoestrogens. A variety of health benefits are associated with the consumption of soy primarily because of the isoflavones genistein, daidzein, and glycitein with a potential protective effect against a number of chronic diseases. Owing to the pharmaceutical and nutraceutical properties allied with isoflavonoids and their use in functional foods, there is a growing interest in these compounds. This review throws light on the chemistry, and significant pharmacological and biopharmaceutical aspects of soy isoflavones. This article critically describes the mechanisms of action, infers conclusions and shows opportunity for future research.

Effects of phyto-oestrogens on tissues

Recent investigations on the effects of phyto-oestrogens on various tissues have revealed that these diverse molecules may improve human health, particularly by protecting against certain chronic diseases. After a brief examination of the food sources, structures, and general cellular actions of the major phyto-oestrogens, current research findings on cardiovascular disease, skeletal tissues, and reproductive cancers are reviewed. Phyto-oestrogen concentrations in blood may be maintained at high levels in those consuming soyabean (Glycine max)-based food daily at several meals and exert their effects on target cells through either genomic effects via the classical oestrogen receptors or non-genomic effects mediated by membrane-bound oestrogen receptors or other cellular proteins. The expression of oestrogen receptor (OR) subtypes alpha (a) and beta (beta) varies across tissues, and cells that preferentially express OR-beta, which may include bone cells, are more likely to respond to phyto-oestrogens. Conversely, reproductive tissues contain relatively more OR-a and may, thus, be differently affected by phyto-oestrogens. Soyabean phyto-oestrogens appear to prevent the progression of atherosclerosis through multiple interactions, including lowering of plasma lipids and lipoproteins, increased vasodilatation and, possibly, decreased activation of blood platelets and vascular smooth muscle cells. However, a favourable impact on cardiovascular disease morbidity and mortality by a soyabean-enriched western-type diet remains to be shown, and unresolved questions remain regarding dose and form of the phyto-oestrogens in relation to risks and benefits. The isoflavones of soyabean have been shown consistently to have bone-retentive effects in animal studies by several investigators using rodent models, although intakes must be above a relatively high threshold level for a lengthy period of time, and little or no extra benefit is observed with intakes above this threshold level. The reports of modest or no effects on prevention of bone loss in human and non-human primate studies respectively, may be due to the limited doses tested so far. The relationship between soyabean-food intake and cancer risk has been more extensively investigated than for any other disease, but with less certainty about the benefits of long-term consumption of phyto-oestrogen-containing foods on prevention of cancer. The observations that breast and prostate cancer rates are lower in Asian countries, where soyabean foods are consumed at high levels, and the high isoflavone content of soyabeans have led to examination of the potential protective effects of phyto-oestrogens. Establishing diet-cancer relationships has proved difficult, in part because of the conflicting data from various studies of effects of soyabean-diets on cancer. Epidemiological evidence, though not impressive, does suggest that soyabean intake reduces breast cancer risk. The isoflavone genistein has a potent effect on breast cancer cells in vitro, and early exposure of animals to genistein has been effective in reducing later development of mammary cancer. Thus, continuous consumption of soyabean foods in early life and adulthood may help explain the low breast cancer mortality rates in Asian countries. Although the evidence for a protective effect against prostate cancer may be slightly more supportive, more research is needed before any firm conclusions can be made about the phyto-oestrogen-cancer linkages.

Soy-diet has beneficial effects on cardiovascular parameters that are independent of its lipid effect in male hypercholesterolemic rats

Diet-induced atherosclerosis is lower in animals fed soy protein. The effects of various soy components have been extensively studied; however, little is known about the effect of crude soybean feeding on hypercholesterolemia-induced cardiovascular changes. This study investigated the effect of soy feeding on cardiovascular parameters in hypercholesterolemic male rats. Total cholesterol (TC), low density lipoprotein (LDL) and high density lipoprotein cholesterol (HDL), and triglyceride (TG) were measured. Rats were randomly assigned to control, high cholesterol (HC, 2% cholesterol) or HC + soy (HC+S) diets. In the HC+S group, rats received HC diet for 10 weeks followed by 2 weeks of soybean feeding. Arterial blood pressure, TC, TG, LDL and HDL were measured. TC, TG and LDL were higher in HC rats and were not significantly reduced by soybean feeding. Soy feeding reversed the HC-induced increase in arterial blood pressure and also restored the impaired vascular responses to acetylcholine in isolated aortic rings. Pre-incubation of HC+S aortic rings with L-NAME (10(-5) M for 20 min) partially reduced the effects of soy on acetylcholine responses, indicating that the beneficial vascular effects of dietary soy are partially mediated via nitric oxide pathway.

Genistein inhibits the development of atherosclerosis via inhibiting NF-κB and VCAM-1 expression in LDLR knockout mice

Diet can be an important factor that influences risks for cardiovascular disease. Genistein (4′,5,7-trihydroxyisoflavone), rich in soy, is one candidate that may benefit the cardiovascular system. Here, we explored the effect of genistein in atherosclerosis (AS) development in an in vivo mouse model. Low-density lipoprotein receptor (LDLR) knockout mice were allocated to control, model, and genistein groups. Our results showed that genistein significantly reduced the formation and development of atherosclerotic plaques ((4.68 ± 1.18) ×106 versus (6.65 ± 1.51) ×106 µm2, p < 0.05). In the genistein group, compared with the model group, total antioxidant capacity (TAC) level was 85.5 ± 15.6 versus 203.4 ± 32.6 mmol/L (p < 0.01); malondialdehyde (MDA) level was 3.79 ± 0.28 versus 3.06 ± 0.31 mmol/L (p < 0.01), and superoxide dismutase (SOD) activity was 86.1 ± 6.1 versus 139.1 ± 25.1 U/mL (p < 0.01). Therefore, genistein was able to enhance serum antioxidative ability in our mouse model. Genistein had no influence, however, on serum cholesterol and lipid profiles. Genistein also markedly downregulated the expression of nuclear factor (NF)-κB and vascular cell adhesion molecule (VCAM)-1 in aortas of mice (p < 0.05). These observations suggest that genistein may inhibit AS in LDLR−/− mice via enhancing serum antioxidation and downregulating NF-κB and VCAM-1 expression in the aorta.

Novel anti-inflammatory mechanisms of N-Acetyl-Ser-Asp-Lys-Pro in hypertension-induced target organ damage

High blood pressure (HBP) is an important risk factor for cardiac, renal, and vascular dysfunction. Excess inflammation is the major pathogenic mechanism for HBP-induced target organ damage (TOD). N-acetyl-Ser-Asp-Lys-Pro (Ac-SDKP), a tetrapeptide specifically degraded by angiotensin converting enzyme (ACE), reduces inflammation, fibrosis, and TOD induced by HBP. Our hypothesis is that Ac-SDKP exerts its anti-inflammatory effects by inhibiting: 1) differentiation of bone marrow stem cells (BMSC) to macrophages, 2) activation and migration of macrophages, and 3) release of the proinflammatory cytokine TNF-alpha by activated macrophages. BMSC were freshly isolated and cultured in macrophage growth medium. Differentiation of murine BMSC to macrophages was analyzed by flow cytometry using F4/80 as a marker of macrophage maturation. Macrophage migration was measured in a modified Boyden chamber. TNF-alpha release by activated macrophages in culture was measured by ELISA. Myocardial macrophage activation in mice with ANG II-induced hypertension was studied by Western blotting of Mac-2 (galectin-3) protein. Interstitial collagen deposition was measured by picrosirius red staining. We found that Ac-SDKP (10 nM) reduced differentiation of cultured BMSC to mature macrophages by 24.5% [F4/80 positivity: 14.09 +/- 1.06 mean fluorescent intensity for vehicle and 10.63 +/- 0.35 for Ac-SDKP; P < 0.05]. Ac-SDKP also decreased galectin-3 and macrophage colony-stimulating factor-dependent macrophage migration. In addition, Ac-SDKP decreased secretion of TNF-alpha by macrophages stimulated with bacterial LPS. In mice with ANG II-induced hypertension, Ac-SDKP reduced expression of galectin-3, a protein produced by infiltrating macrophages in the myocardium, and interstitial collagen deposition. In conclusion, this study demonstrates that part of the anti-inflammatory effect of Ac-SDKP is due to its direct effect on BMSC and macrophage, inhibiting their differentiation, activation, and cytokine release. These effects explain some of the anti-inflammatory and antifibrotic properties of Ac-SDKP in hypertension.

Phytoestrogens: end of a tale?

Phytoestrogens are plant-derived hormone-like diphenolic compounds of dietary origin that are present at high levels in plasma of subjects living in areas with low atherosclerosis and cancer incidence. The term phytoestrogen is commonly applied to the soy isoflavones genistein, daidzein and glycitein. As outlined in a previous review article in this journal by Adlercreutz and Mazur 1, these compounds are weakly estrogenic and appear to influence the cardiovascular system, the production, metabolism and biological activity of sex-hormones, as well as malignant cell proliferation, differentiation and angiogenesis. Recently skepticism has developed concerning the true potential of phytoestrogens to beneficially modify these processes. A critical analysis of the early findings from supplementing the diet with soy protein has failed to confirm phytoestrogens as the responsible agent for beneficial cardiovascular effects, be it by way of lipid reduction, vasodilation or lipoprotein oxidation. Furthermore, contrasting data have been reported on the potential of phytoestrogens to prevent hormone-dependent cancers (e.g. breast and prostate) and to successfully treat post-menopausal complaints, an indication for which they are widely used. These potentially negative findings have led health authorities in several countries to suggest maximum daily intake levels for phytoestrogens. There is now growing interest in the use of soy products containing low levels of phytoestrogens and in research on other phytoestrogen free legumes such as lupin.

Role of E2F and ERK1/2 in STI571-mediated smooth muscle cell growth arrest and cyclin A transcriptional repression

Platelet-derived growth factor (PDGF) ligand and receptors (PDGF-R) activate smooth muscle cell (SMC) proliferation, a key event during vascular obstructive disease. The PDGF-R tyrosine kinase inhibitor STI571 attenuates SMC proliferation and experimental neointimal thickening. Here, we investigated the molecular mechanisms underlying STI571-dependent SMC growth arrest. STI571 abrogates PDGF-BB-dependent cyclin D1 and cyclin A protein expression and inhibits transcriptional activation of reporter genes driven by the human cyclin A gene promoter. Repression of cyclin A promoter activity by STI571 requires a functional E2F-binding site, and forced expression of E2F overrides this inhibitory effect. Moreover, STI571 inhibits E2F DNA-binding activity in SMCs. We also found that STI571 abrogates PDGF-BB-dependent activation of extracellular-regulated kinase 1 and 2 (ERK1/2), and forced activation of these factors impaired STI571-dependent inhibition of both cyclin A promoter activity and SMC proliferation. Thus, E2F and ERK1/2 play an important role in STI571-mediated SMC growth arrest and cyclin A transcriptional repression. These findings may have importance in the development of novel therapeutic strategies for the treatment of neointimal hyperplasia.

Soy protein with isoflavones has favorable effects on endothelial function that are independent of lipid and antioxidant effects in healthy postmenopausal women

BACKGROUND

Controversy exists about the ability of soy protein and isoflavones to modulate vascular reactivity and biochemical cardiovascular disease risk markers in healthy, normolipidemic postmenopausal women.

OBJECTIVE

The objective was to investigate whether the consumption of soy protein with isoflavones would result in improved vascular reactivity and decreased biochemical markers of endothelial dysfunction and inflammation, independent of enhanced lipid and antioxidant effects.

DESIGN

Healthy postmenopausal women (n = 28) were enrolled in a randomized, double-blind, crossover study, and they consumed 25 g of 3 protein products/d for 6 wk each, with intervening washout periods. The products were isolated soy protein with isoflavones, ethanol-washed isolated soy protein with trace isoflavones, and total milk protein, which supplied 107, 2, and 0 mg total isoflavone (aglycone) units/d, respectively. We studied vascular function by using brachial artery reactivity values, plasma concentrations of vasoactive factors, endothelial inflammatory markers, and plasma isoflavone concentrations. The resistance of whole plasma and isolated LDL to copper-mediated oxidation was measured by conjugated diene formation.

RESULTS

Postocclusion peak flow velocity of the brachial artery was significantly (P = 0.03) lower after treatment with isolated soy protein with isoflavones, which is consistent with a vasodilatory response, than after treatment with total milk protein. Plasma isoflavones and metabolites were significantly (P < 0.01) higher after treatment with isolated soy protein with isoflavones. There were no significant changes in biochemical cardiovascular disease risk markers or conjugated diene formation between the 3 dietary groups.

CONCLUSION

Daily consumption of soy protein with isoflavones can result in positive vascular effects that are independent of lipid and antioxidant effects in healthy postmenopausal women.

Soy isoflavones prevent ovariectomy-induced atherosclerotic lesions in Golden Syrian hamster model of postmenopausal hyperlipidemia

OBJECTIVE

Soy isoflavones, as dietary supplements, may reduce the formation of atherosclerotic lesions that increase in women after menopause. The objectives of this study were to determine whether (1) ovariectomized (ovx) hamsters will develop atherosclerotic lesions and (2) soy isoflavones can dose-dependently prevent the ovariectomy-induced rise in plasma cholesterol and atherosclerotic lesions in hamsters.

DESIGN

Seventy-two 6-month-old female Golden Syrian hamsters were randomly assigned to six groups: sham-operated; ovx control; ovx + 17beta-estradiol (E(2); 10 microg E(2) per kilogram of body weight); and ovx + 9.5 (low-dose), 19 (medium-dose), or 38 (high-dose) mg isoflavones per kilogram diet. Treatments were initiated immediately after surgery and continued for 120 days. Blood was drawn via abdominal aorta for assessment of circulating lipids, and tissues were collected, including the aortic arch for assessment of atherosclerotic lesions.

RESULTS

All three doses of isoflavones prevented the rise in plasma total cholesterol from ovx; and, as the isoflavone dose increases, the cholesterol-lowering effects of isoflavones become more pronounced (7.8%, 11.8%, and 19.6% reductions in total cholesterol for low-dose, medium-dose, and high-dose, respectively). Ovx hamsters developed atherosclerotic lesions without being on an atherogenic diet. Ninety-two percent of hamsters in the ovx control group had atherosclerotic lesions compared with only 8% in sham, 62% in the E(2) group, 29% in the low-dose group, 38% in the medium-dose group, and 58% in the high-dose group. The aortic fatty streak area was approximately 20 times higher in ovx hamsters compared with the sham animals. All doses of isoflavones were able to significantly reduce fatty streak area to that of the sham group.

CONCLUSIONS

Soy isoflavones, independent of the protein source, prevent hypercholesterolemia and the formation of atherosclerotic lesions induced by ovarian hormone deficiency in hamsters. The antiatherogenic mechanisms of isoflavones need further investigation.

Risks and benefits of soy phytoestrogens in cardiovascular diseases, cancer, climacteric symptoms and osteoporosis

Phytoestrogens, plant chemicals classified as isoflavones, coumestans and lignans, display estrogen-like activity because of their structural similarity to human estrogens and exhibit high affinity binding for the estrogen receptor beta. They are common components of food items such as grains, beans, fruits and nuts. Isoflavones are primarily found in soybeans and foods made from soy. In particular, significant therapeutic properties have been generally attributed to soy isoflavones, but most of the claims have been poorly, or not at all, confirmed by well designed clinical trials. Such is the case of the purported role of soy isoflavones in reducing plasma cholesterol levels. This link is now not supported by many authors or by appropriately designed clinical studies. The role of isoflavones in cancer prevention, particularly of tumours under endocrine control (breast, prostate and others) is again only supported by weak to nonexisting clinical evidence. A similarcase is that of the prevention/treatment of postmenopausal symptoms and osteoporosis. Disturbing data have been reported on potential negative effects of soy isoflavones on cognitive function in the aged, particularly relating to tofu intake. Recent studies have finally indicated a potential role for soy isoflavones in inducing chromosomal changes in cells exposed in vitro and potentiating chemical carcinogens. These findings may not, however, be extrapolated to clinical conditions. Available data do not appear to unequivocally support beneficial effects of soy isoflavones, and warn against their wide use, in the absence of satisfactory clinical findings.

Isoflavone aglycone-rich extract without soy protein attenuates atherosclerosis development in cholesterol-fed rabbits

The antiatherogenic effect of soy protein with intact isoflavones is well established, but the effects of isoflavones without soy protein have not been determined. We investigated the antiatherogenic effect of an isoflavone aglycone-rich extract (containing 429.4 mg/g isoflavone aglycones) without soy protein from fermented soy in cholesterol-fed rabbits. We fed 12-wk-old New Zealand white male rabbits diets containing 1 g/100 g cholesterol with 0, 0.33 or 1 g/100 g isoflavone aglycones for 8 wk. We also fed the rabbits a diet containing 1 g/100 g cholesterol with 1.09 g/100 g soy saponin-rich extract, a component other than isoflavone aglycones in the isoflavone aglycone-rich extract. Controls did not consume cholesterol, isoflavone aglycones or saponins. The isoflavone aglycone- and saponin-rich extracts did not affect the serum lipid profile of cholesterol-fed rabbits. The serum concentration of daidzein in its conjugated form was significantly higher in the high isoflavone group than in the low isoflavone group. The level of cholesteryl ester hydroperoxide (ChE-OOH) induced by CuSO(4) in plasma in the high isoflavone group was significantly less than that in the cholesterol group, and the ChE-OOH levels of LDL in the low and high isoflavone groups were significantly less than those in the cholesterol group. The ChE-OOH levels in plasma and LDL in the saponin group did not differ from the cholesterol group. In the aortic arch, the cholesterol concentration was significantly lower in the high isoflavone group, and malondialdehyde concentration was significantly lower in the low and high isoflavone groups compared with the cholesterol group; however these concentrations in the saponin group did not differ from those in the cholesterol group. The atherosclerotic lesion area of the aortic arch was significantly lower in the isoflavone groups (26.3% lower in the low isoflavone group and 36.9% lower in the high isoflavone group) than in the cholesterol group. The lesion areas were not different in the soy saponin and cholesterol groups. Immunohistochemical analysis revealed fewer oxidized LDL-positive macrophage-derived foam cells in atherosclerotic lesions in the aortic arch of isoflavone groups compared with that of the cholesterol group. These results suggest that the antioxidative action of isoflavones and their antioxidative metabolites inhibit the oxidation of LDL, thereby exerting an antiatherosclerotic effect.

Dietary soy-derived isoflavone phytoestrogens. Could they have a role in coronary heart disease prevention?

Soy protein-containing foods are a rich source of isoflavone phytoestrogens, such as genistein and daidzein. There is great interest in these substances, as lower rates of chronic diseases, including coronary heart disease, have been associated with high dietary intake of soy-containing foods. Soy phytoestrogens bind weakly to estrogen receptors, and some bind more strongly to estrogen receptor-beta compared with estrogen receptor-alpha. A meta-analysis has indicated that isoflavone phytoestrogens lowered plasma cholesterol concentrations in subjects with initially elevated levels, but had little effect in subjects with normal cholesterol concentrations. These substances reportedly may also have beneficial effects on arterial endothelial function. In addition to these potentially antiatherogenic effects, many laboratories are investigating other possible mechanisms, including antioxidative and antiproliferative properties of these substances. We have shown that dietary supplementation with soy-derived isoflavones reduced the in vitro oxidation susceptibility of low-density lipoprotein (LDL). To further explore this phenomenon, we incorporated genistein and daidzein into LDL molecules in vitro with the aid of an artificial transfer system. However, it was necessary to convert the isoflavone molecules to fat-soluble derivatives, fatty acid esters (analogous to esterified endogenous estrogens, which are known to occur in vivo), to achieve significant incorporation. The LDLs containing esterified isoflavones were shown to be less susceptible to oxidation in vitro than native LDL. We also employed U937 cell cultures for investigating the effects of isoflavone-containing LDLs on cell proliferation. Some of these LDLs exhibited antiproliferative effects in cultured U937 cells. In summary, lipophilic phytoestrogen derivatives could be incorporated into LDLs, increasing their oxidation resistance and antiproliferative efficacy ex vivo, both of which are, in theory, antiatherogenic effects. Further studies are needed to assess to what extent analogous effects could be produced in vivo and whether such substances have a role in hormone replacement and coronary heart disease prevention in postmenopausal women.

The role of protein-tyrosine phosphorylation and gelatinase production in the migration and proliferation of smooth muscle cells

BACKGROUND

It has been reported that matrix metalloproteinase (MMP) was expressed in coronary arterial atherosclerotic lesions. However, not much is known about the relationship between the production of MMP and the progression of atherosclerosis.

PURPOSE AND METHOD

To demonstrate the association between the protein-tyrosine phosphorylation (PTP) and the activation of extracellular MMP in the proliferation and migration of vascular smooth muscle cells (VSMCs), the effect of platelet-derived growth factor (PDGF) and vanadate (an inhibitor of protein-tyrosine phosphatase and an activator of certain protein-tyrosine kinases) on mitogenesis ([3H]thymidine incorporation after 24 hours), migration, PTP (Western blot analysis using anti-phosphotyrosine antibodies), and production of MMP (gelatin zymography) was examined in cultured VSMCs.

RESULTS

Both vanadate (1-5 micromol/l) and PDGF (1-10 ng/ml) caused a dose-dependent increase in thymidine incorporation and migration and produced 72-kDa type IV gelatinase (MMP-2) in VSMCs. The combination of vanadate and PDGF resulted in a dose-dependent synergistic effect on thymidine incorporation and MMP-2 production. Western blot analysis revealed that PDGF caused an increase in PTP, extracellular signal-regulated kinases (ERK1, ERK2) and PDGF receptor in VSMCs. Vanadate given together with PDGF induced a marked increase in the intensity of tyrosine phosphorylation in these proteins. Tyrosine kinase inhibitors (genistein and herbimycin A) and a synthetic inhibitor of MMP (1,10-phenanthroline) and an anti-MMP-2 neutralizing antibody inhibited the mitogenic effect induced by vanadate and/or PDGF.

CONCLUSIONS

The data suggest that the proliferation and migration of cultured VSMCs was closely related to the stimulation of MMP-2 production that was induced through activation of PTK.

Health potential of soy isoflavones for menopausal women

OBJECTIVE

To review the current literature on the effects of soy isoflavones, one class of phyto-oestrogens, on cardiovascular diseases, osteoporosis, cancer and climacteric symptoms.

DESIGN

Many study designs were employed in the reports reviewed here, including prospective human trials, observational human studies, animal experiments and in vitro cell studies that explored the protective or preventive effects of soy isoflavones (genistein, daidzein and glycitein alone or mixed).

SETTING

Diverse settings were employed, depending on study design.

SUBJECTS

Human subjects, mostly menopausal or postmenopausal, were included, as were animal models and specific cell types.

RESULTS

The findings were: (i) isoflavones plus soy protein together were needed to obtain the highly significant beneficial results on blood lipids and arterial dimensions; (ii) isoflavone treatments alone at high doses (relative to above) consistently improved bone parameters in rodent ovariectomized models, but not in humans or primates; (iii) isoflavones were not consistent in exerting positive effects regarding the prevention or treatment of cancers of the mammary glands, uterus and colon; and (iv) the effects of isoflavones on climacteric symptoms were not clear-cut.

CONCLUSIONS

The promise of soy isoflavones reducing chronic disease risk seems to be non-uniform, with the most conclusive benefits occurring in the prevention of cardiovascular diseases, but other organ systems, such as skeletal and reproductive tissues, may also benefit from the consumption of soy and soy-derived products.

Phytoestrogens. State of the art

A short overview of recent advances of phytoestrogen research is presented. Developments have particularly been made with regard to methods, food analyses, pharmacokinetics, receptor studies, mechanisms of action and effects on cancer. Most studies deal with isoflavones, but the interest in lignans is increasing as a result of a large rye project in the Nordic countries. The development of rapid time-resolved immunofluorescence assays in 20 μl plasma samples for enterolactone, genistein and daidzein has resulted in the initiation of many prospective studies on cancer risk using blood bank material.

Ethanol inhibits basal and flow-induced vascular smooth muscle cell migration in vitro

BACKGROUND

Alcohol consumption protects against coronary heart disease by as yet unclear mechanisms. The aim of this study was to determine the effect of ethanol on vascular smooth muscle cell (SMC) migration which plays an important role in the pathogenesis of atherosclerosis.

MATERIALS AND METHODS

Cultures of human SMC under static (no flow) or pulsatile flow conditions (perfused transcapillary culture system) were pretreated in the absence or presence of ethanol (EtOH) whereupon their random migration (chemokinesis) was assessed by Transwell assay.

RESULTS

Ethanol pretreatment (24 h) dose dependently inhibited migration of HuSMC from static cultures with a maximal inhibition of 60.8 +/- 4.4% observed at 40-80 mM, in the absence of any effect on cell adhesion or cell viability as assessed by trypan blue exclusion. In HuSMC exposed to pulsatile flow (0.3 to 25 ml/min, 24 h), there was a flow-dependent increase in migration ranging from a 1.3 +/- 0.16- to 2.67 +/- 0.26-fold increase, compared to static cells, concomitant with a significant increase in urokinase-type plasminogen activator (uPA) mRNA levels. Ethanol pretreatment (20-80 mM, 24 h) dose dependently inhibited the flow-induced increase in SMC migration but did not affect uPA mRNA expression.

CONCLUSIONS

The inhibitory effect of ethanol on basal and flow-stimulated SMC migration may be relevant to its cardiovascular effects in vivo.

Local inhibition of tyrosine kinase activity markedly attenuates the development of intimal hyperplasia in experimental vein grafts

BACKGROUND

Intimal hyperplasia is due to the migration and proliferation of vascular smooth muscle cells after bypass surgery. Tyrosine kinases are involved in many signal transduction pathways including cell proliferation. This study examines the effects of local treatment with the tyrosine kinase inhibitor, tyrphostin AG-51, on the formation of intimal hyperplasia in vein grafts.

MATERIALS AND METHODS

Thirty-nine New Zealand White rabbits underwent interposition bypass grafting of the carotid artery using the jugular vein. In the first group (TKI), tyrphostin AG-51 (5 mg), dissolved in 600 microliter of dimethyl sulfoxide and Ringer's lactate (2:1, v:v), was used to incubate the veins ex vivo prior to grafting and delivered locally in 2.5 ml of 30% pluronic gel after grafting. The second group (DMSO) received the same treatment but without tyrphostin. In the third group (control), tyrphostin and DMSO were omitted from the incubation and gel delivery solutions. Postoperatively, vein grafts were harvested on Day 3 for Western analysis using an antiphosphotyrosine antibody (PY-20) to assess for tyrosine kinase activity, and on Day 28 for either morphologic or contractile function studies.

RESULTS

Local application of the TKI to vein grafts resulted in a 49% reduction in intimal hyperplasia compared to DMSO-treated vein grafts (31 +/- 4 micrometer vs. 61 +/- 5 micrometer, P < 0.01). Treatment with DMSO alone reduced intimal hyperplasia by 28% compared to control (85 +/- 4 micrometer, P < 0.05). The contractile responses in the DMSO and TKI-treated vein grafts were equivalent. Western analysis showed a 39-fold decrease in tyrosine phosphorylation with TKI treatment compared to control.

CONCLUSION

This study demonstrates that local short-term treatment with TKI produces a 49% reduction in intimal hyperplasia and suggests that phosphorylation of tyrosine residues is involved in the signaling pathways leading to the development of intimal hyperplasia in vein grafts.

Phyto-oestrogens and Western diseases

Incidences of breast, colorectal and prostate cancer are high in the Western world compared to countries in Asia. We have postulated that the Western diet compared to the semivegetarian diet in some Asian countries may alter hormone production, metabolism or action at the cellular level by some biochemical mechanisms. Our interest has been focused on two groups of hormone-like diphenolic phyto-oestrogens of dietary origin, the lignans and isoflavonoids abundant in plasma of subjects living in areas with low cancer incidence. The precursors of the biologically active compounds detected in man are found in soybean products, whole-grain cereal food, seeds, and berries. The plant lignan and isoflavonoid glycosides are converted by intestinal bacteria to hormone-like compounds. The weakly oestrogenic diphenols formed influence sex-hormone production, metabolism and biological activity, intracellular enzymes, protein synthesis, growth factor action, malignant cell proliferation, differentiation, cell adhesion and angiogenesis in such a way as to make them strong candidates for a role as natural cancer-protective compounds. Their effect on some of the most important steroid biosynthetic enzymes may result in beneficial modulation of hormone concentrations and action in the cells preventing development of cancer. Owing to their oestrogenic activity they reduce hot flushes and vaginal dryness in postmenopausal women and may to some degree inhibit osteoporosis, but alone they may be insufficient for complete protection. Soy intake prevents oxidation of the low-density lipoproteins in vitro when isolated from soy-treated individuals and affect favourably plasma lipid concentrations. Animal experiments provide evidence suggesting that both lignans and isoflavonoids may prevent the development of cancer as well as atherosclerosis. However, in some of these experiments it has not been possible to separate the phyto-oestrogen effect from the effect of other components in the food. The isoflavonoids and lignans may play a significant inhibitory role in cancer development particularly in the promotional phase of the disease, but recent evidence points also to a role in the initiation stage of carcinogenesis. At present, however, no definite recommendations can be made as to the dietary amounts needed for prevention of disease. This review deals with all the above-mentioned aspects of phyto-oestrogens.

The tyrosine kinase inhibitor methyl 2,5-dihydroxycinnimate disrupts changes in the actin cytoskeleton required for neurite formation

In the current studies, we investigated the relationship between tyrosine phosphorylation and neurite formation. In SH-SY5Y neuroblastoma cells, the tyrosine kinase inhibitor methyl 2, 5-dihydroxycinnimate blocked neurite formation on laminin. This corresponded with inhibition of paxillin and focal adhesion kinase tyrosine phosphorylation as well as a disruption of actin filament organization and actin polymerization. This suggests that tyrosine phosphorylation helps direct changes in the actin cytoskeleton required for neurite formation.

Phosphatidylinositol 3-kinase-independent signal transduction pathway for platelet-derived growth factor-induced chemotaxis

Platelet-derived growth factor (PDGF)-BB is a potent chemoattractant for mesenchymal cells. Intracellular signal transduction for PDGF-induced chemotactic response has been reported to be dependent on phosphatidylinositol 3-kinase (PI3K) activation. Here, we report a PI3K-independent pathway operating for PDGF-induced chemotaxis in vascular smooth muscle cells and other cell types. Two different PI3K inhibitors, wortmannin (WT, 1 nM-1 microM) and LY294002 (100 nM-10 microM), did not inhibit PDGF-induced chemotaxis in smooth muscle cells and Swiss 3T3 cells, whereas WT inhibited activity of PI3K that were immunopurified from PDGF-stimulated cells as well as PI3K purified from cells that were stimulated with PDGF in the presence of the same concentrations of WT. Similarly, WT (100 nM) abolished the increase in intracellular phosphatidylinositol 3,4,5-triphosphate after PDGF stimulation. Furthermore, Chinese hamster ovary/Deltap85 cells overexpressing a dominant negative p85 subunit of PI3K showed a chemotactic response comparable to that of parental cells while showing a remarkable decrease in PI3K activity. Rapamycin, a specific inhibitor of pp70 S6 kinase, which is one of the well characterized downstreams of PI3K, did not inhibit PDGF-induced chemotaxis. Both WT and LY294002 inhibited PDGF-induced amino acid uptake and actin-stress fiber reorganization and partly inhibited PDGF-induced glucose incorporation in Swiss 3T3 cells. Our findings indicate that, in vascular smooth muscle cells and other cell types, the signal transduction for PDGF-induced chemotaxis is independent of PI3K activity while the signal transduction for PDGF-induced amino acid uptake, glucose incorporation, and cytoskeletal reorganization is dependent on PI3K.

Controlled delivery of a tyrphostin inhibits intimal hyperplasia in a rat carotid artery injury model

We examined the inhibitory effect of AG-17, a potent inhibitor of protein tyrosine kinase activity on injury-induced vascular SMC proliferation by polymeric-based, periadventitial controlled release implant in the balloon catheter carotid injury model in rats. The AG-17 delivery system was formulated from ethylenevinyl acetate copolymer and the release kinetics as well as drug stability were determined. Polymeric matrices containing 2 or 10% AG-17 were implanted perivascularly in rats following balloon catheter injury. Western blot analysis of explanted arterial segments revealed enhanced tyrosine phosphorylation in injured arteries that was essentially reduced to normal levels in treated arteries. The mean neointima to media ratios were significantly reduced in both 2% (0.79 +/- 0.17, n = 9, P < 0.02) and 10% AG-17 (0.59 +/- 0.09, n = 12, P < 0.001) groups in comparison to the control group (1.38 +/- 0.18, n = 16). The mean areas of the media in the control and the 2% AG-17 group did not differ significantly but a significant reduction of the mean area of the media was observed in 10% AG-17 group. Embedding of the unstable tyrphostin compound, AG-17, in a hydrophobic matrix stabilizes the drug both in vitro and in vivo, and allows delivery-rate modulation as well as protracted site-specific therapy. Perivascular controlled release delivery of the tyrphostin AG-17 inhibits neointimal formation in the rat carotid injury model.

YopH of Yersinia pseudotuberculosis interrupts early phosphotyrosine signalling associated with phagocytosis

The PTPase YopH of Yersinia is essential to the ability of these bacteria to block phagocytosis. Wild-type Yersinia pseudotuberculosis, but not the yopH mutant strain, resisted phagocytosis by J774 cells. Ingestion of a yopH mutant was dependent on tyrosine kinase activity. Transcomplementation with wild-type yopH restored the anti-phagocytic effect, whereas introduction of the gene encoding the catalytically inactive yopHC403A was without effect. The PTPase inhibitor orthovanadate impaired the anti-phagocytic effect of the wild-type strain, further demonstrating the importance of bacteria-derived PTPase activity for this event. The ability to resist phagocytosis indicates that the effect of the bacterium is immediately exerted when it becomes associated with the phagocyte. Within 30 s after the onset of infection, wild-type Y. pseudotuberculosis caused a YopH-dependent dephosphorylation of phosphotyrosine proteins in J774 cells. Furthermore, interaction of the cells with phagocytosable strains led to a rapid and transient increase in tyrosine phosphorylation of paxillin and some other proteins, an event dependent on the presence of the bacterial surface-located protein invasin. Co-infection with the phagocytosable strain and the wild-type strain abolished the induction of tyrosine phosphorylation. Taken together, the present findings demonstrate an immediate YopH-mediated dephosphorylation of macrophage phosphotyrosine proteins, suggesting that this PTPase acts by preventing early phagocytosis-linked signalling in the phagocyte.

Inhibition of PDGF- and TGF-beta 1-induced collagen synthesis, migration and proliferation by tranilast in vascular smooth muscle cells from spontaneously hypertensive rats

Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) proliferate faster and are more sensitive to transforming growth factor-beta 1 (TGF-beta 1) than those of normotensive Wistar-Kyoto rats. We studied the in vitro effects of tranilast, an anti-allergic drug, on the proliferation, migration and extracellular matrix synthesis in the SHR-VSMC. There were many inhibitory effects of tranilast (30-300 microM) on SHR-VSMC. One is the effect on the proliferation stimulated with fetal bovine serum (FBS), TGF-beta 1 and platelet-derived growth factor-BB (PDGF-BB). Another is the effect on the PDGF-BB-induced migration. Lastly, tranilast exhibited inhibitory effects on spontaneous collagen synthesis and TGF-beta 1-induced collagen and glycosaminoglycan synthesis. On the other hand, collagen induced the VSMC migration concentration-dependently. These results suggest that tranilast may prevent restenosis after percutaneous transluminal coronary angioplasty.

Yersinia pseudotuberculosis inhibits Fc receptor-mediated phagocytosis in J774 cells

Nonopsonized as well as immunoglobulin-G (IgG)-opsonized Yersinia pseudotuberculosis resists phagocytic uptake by the macrophage-like cell line J774 by a mechanism involving the plasmid-encoded proteins Yops. The tyrosine phosphatase YopH was of great importance for the antiphagocytic effect of the bacteria. YopH-negative mutants did not induce antiphagocytosis; instead, they were readily ingested, almost to the same extent as that of the translocation mutants YopB and YopD and the plasmid-cured strain. The bacterial determinant invasin was demonstrated to mediate phagocytosis of nonopsonized bacteria by these cells. In addition to inhibiting uptake of itself, Y. pseudotuberculosis also interfered with the phagocytic uptake of other types of prey: J774 cells that had been exposed to virulent Y. pseudotuberculosis exhibited a reduced capacity to ingest IgG-opsonized yeast particles. This effect was impaired when the bacterium-phagocyte interaction occurred in the presence of gentamicin, indicating a requirement for in situ bacterial protein synthesis. The Yersinia-mediated antiphagocytic effect on J774 cells was reversible: after 18 h in the presence of gentamicin, the phagocytic capacity of Yersinia-exposed J774 cells was completely restored. Inhibition of the uptake of IgG-opsonized yeast particles was dependent on the Yops in a manner similar to that seen for blockage of Yersinia phagocytosis. This similarity suggests that the pathogen affected a general phagocytic mechanism. Despite a marked reduction in the capacity to ingest IgG-opsonized yeast particles, no effect was observed on the binding of the prey. Taken together, these results demonstrate that Yop-mediated antiphagocytosis by Y. pseudotuberculosis affects regulatory functions downstream of the phagocytic receptor and thereby extends to other types of phagocytosis.

Isolation and biological activities of signal transduction inhibitors from microorganisms and plants

Microorganisms and plants are treasuries of secondary metabolites having unique structures and biological activities. We have isolated inhibitors of cellular signal transduction from them. Phosphatidylinositol turnover inhibitors include inostamycin, piericidins and echiguanines. Erbstatin and lavendustin A were isolated as tyrosine kinase inhibitors, and dephostatin was isolated as a tyrosine phosphatase inhibitor. Recently, we have isolated a new vinca alkaloid having anti-ras activity. These signal transduction inhibitors will be useful for mechanistic studies and suppression of cancer.