Effect of estrogen on vascular smooth muscle cells is dependent upon cellular phenotype

Primary Mouse Aortic Smooth Muscle Cells Exhibit Region- and Sex-Dependent Biological Responses In Vitro

Despite advancements in elucidating biological mechanisms of cardiovascular remodeling, cardiovascular disease (CVD) remains the leading cause of death worldwide. When stratified by sex, clear differences in CVD prevalence and mortality between males and females emerge. Regional differences in phenotype and biological response of cardiovascular cells are important for localizing the initiation and progression of CVD. Thus, to better understand region and sex differences in CVD presentation, we have focused on characterizing in vitro behaviors of primary vascular smooth muscle cells (VSMCs) from the thoracic and abdominal aorta of male and female mice. VSMC contractility was assessed by traction force microscopy (TFM; single cell) and collagen gel contraction (collective) with and without stimulation by transforming growth factor-beta 1 (TGF-β1) and cell proliferation was assessed by a colorimetric metabolic assay (MTT). Gene expression and TFM analysis revealed region- and sex-dependent behaviors, whereas collagen gel contraction was consistent across sex and aortic region under baseline conditions. Thoracic VSMCs showed a sex-dependent sensitivity to TGF-β1-induced collagen gel contraction (female > male; p = 0.025) and a sex-dependent proliferative response (female > male; p < 0.001) that was not apparent in abdominal VSMCs. Although primary VSMCs exhibit intrinsic region and sex differences in biological responses that may be relevant for CVD presentation, several factors-such as inflammation and sex hormones-were not included in this study. Such factors should be included in future studies of in vitro mechanobiological responses relevant to CVD differences in males and females.

Age-Related Changes in Urethral Structure and Responds to Injury: Single-Cell Atlas of a Rat Model of Vaginal Birth Injury induced Stress Urinary Incontinence

Stress urinary incontinence (SUI) greatly affects the daily life of numerous women and is closely related to a history of vaginal delivery and aging. We used vaginal balloon dilation to simulate vaginal birth injury in young and middle-aged rats to produce a SUI animal model, and found that young rats restored urethral structure and function well, but not the middle-aged rats. To identify the characteristics of cellular and molecular changes in the urethral microenvironment during the repair process of SUI. We profiled 51,690 individual female rat urethra cells from 24 and 48 weeks old, with or without simulated vaginal birth injury. Cell interaction analysis showed that signal networks during repair process changed from resting to active, and aging altered the distribution but not the overall level of cell interaction in the repair process. Similarity analysis showed that muscle, fibroblasts, and immune cells underwent large transcriptional changes during aging and repair. In middle-aged rats, cell senescence occurs mainly in the superficial and middle urothelium due to cellular death and shedding, and the basal urothelium expressed many Senescence-Associated Secretory Phenotype (SASP) genes. In conclusion, we established the aging and vaginal balloon dilation (VBD) model of female urethral cell anatomy and the signal network landscape, which provides an insight into the normal or disordered urethra repair process and the scientific basis for developing novel SUI therapies.

Ovariectomy-Induced Arterial Stiffening Differs from Vascular Aging and is Reversed by GPER Activation

Arterial stiffness is a cardiovascular risk factor and dramatically increases as women transition through menopause. The current study assessed whether a mouse model of menopause increases arterial stiffness in a similar manner to aging, and whether activation of the G protein-coupled estrogen receptor (GPER) could reverse stiffness. Female C57Bl/6J mice were ovariectomized (OVX) at 10 weeks of age or aged to 52 weeks, and some mice were treated with GPER agonists. OVX and aging increased pulse wave velocity to a similar extent independent of changes in blood pressure. Aging increased carotid wall thickness, while OVX increased material stiffness without altering vascular geometry. RNA-Seq analysis revealed that OVX downregulated smooth muscle contractile genes. The enantiomerically pure GPER agonist, LNS8801, reversed stiffness in OVX mice to a greater degree than the racemic agonist G-1. In summary, OVX and aging induced arterial stiffening via potentially different mechanisms. Aging was associated with inward remodeling while OVX induced material stiffness independent of geometry and a loss of the contractile phenotype. This study helps to further our understanding of the impact of menopause on vascular health and identifies LNS8801 as a potential therapy to counteract this detrimental process in women.

Immuno-regenerative biomaterials for in situ cardiovascular tissue engineering - Do patient characteristics warrant precision engineering?

In situ tissue engineering using bioresorbable material implants - or scaffolds - that harness the patient's immune response while guiding neotissue formation at the site of implantation is emerging as a novel therapy to regenerate human tissues. For the cardiovascular system, the use of such implants, like blood vessels and heart valves, is gradually entering the stage of clinical translation. This opens up the question if and to what extent patient characteristics influence tissue outcomes, necessitating the precision engineering of scaffolds to guide patient-specific neo-tissue formation. Because of the current scarcity of human in vivo data, herein we review and evaluate in vitro and preclinical investigations to predict the potential role of patient-specific parameters like sex, age, ethnicity, hemodynamics, and a multifactorial disease profile, with special emphasis on their contribution to the inflammation-driven processes of in situ tissue engineering. We conclude that patient-specific conditions have a strong impact on key aspects of in situ cardiovascular tissue engineering, including inflammation, hemodynamic conditions, scaffold resorption, and tissue remodeling capacity, suggesting that a tailored approach may be required to engineer immuno-regenerative biomaterials for safe and predictive clinical applicability.

Effects of female sex hormones on the development of atherosclerosis

Atherosclerosis and associated pathologies, such as coronary artery disease, peripheral vascular disease, and stroke, are still the leading cause of death in Western society. The impact of female sex hormones on cardiovascular diseases has been studied intensively with conflicting findings. The controversy is mainly due to the differences in groups sampling, animal models used, hormonal treatment regimens, and the data analyzed. In the present article, the results of in vitro and in vivo studies and clinical trials are under review.

The age- and sex-specific composition of atherosclerotic plaques in vascular surgery patients

BACKGROUND AND AIMS

The sex- and age-related differences in the composition of iliofemoral atherosclerotic plaques are largely unknown. Therefore, the aim of the current study is to gain insight into plaque composition across strata of age and sex in a large cohort of vascular surgery patients.

METHODS

Peripheral atherosclerotic plaques of patients who underwent iliofemoral endarterectomy (n = 790) were harvested between 2002 and 2014. The plaques were semi-quantitatively analyzed for the presence of lipid cores, calcifications, plaque hemorrhages (PH), collagen, macrophage and smooth muscle cell (SMC) content, and quantitatively for microvessel density. Patients were stratified by age tertiles and sex.

RESULTS

Ageing was independently associated with rupture-prone iliofemoral plaque characteristics, such as higher prevalence of plaque calcifications (OR 1.52 (95%CI:1.03-2.24) p = 0.035) and PH (OR 1.46 (95%CI:1.01-2.09) p = 0.042), and lower prevalence of collagen (OR 0.52 (95%CI:0.31-0.86) p = 0.012) and SMCs (OR 0.59 (95%CI:0.39-0.90) p = 0.015). Sex-stratified data showed that men had a higher prevalence of lipid cores (OR 1.62 (95%CI:1.06-2.45) p = 0.025) and PH (OR 1.62 (95%CI:1.16-2.54) p = 0.004) compared to women. These sex-differences attenuated with increasing age, with women showing an age-related increase in calcifications (p = 0.002), PH (p = 0.015) and decrease in macrophages (p = 0.005). In contrast, men only showed a decrease in collagen (p = 0.043).

CONCLUSIONS

Atherosclerotic iliofemoral plaques derived from men display more rupture-prone characteristics compared to women. Yet, this difference is attenuated with an increase in age, with older women having more rupture-prone characteristics compared to younger women.

Estrogen in vascular smooth muscle cells: A friend or a foe?

Cardiovascular disease (CVD) continues to be the leading cause of death worldwide. The effect of estrogen on these diseases has been assessed in in vitro and in vivo models, as well as in observational studies. Collectively, these studies alluded to a cardiovasculo-protective effect of estrogen. However, comprehensive clinical investigation failed to produce concrete proof of a cardiovascular protective effect for hormone replacement therapy (HRT), let alone rule out potential harm. These seemingly paradoxical effects of estrogen were explained by the 'theory of timing and opportunity'. This theory states that the effect of estrogen, whether cardiovasculo-protective or pathological, significantly depends on the age of the individual when estrogen administration takes place. Here, we review the conflicting effects of estrogen on vascular smooth muscle cells, mainly proliferation and migration as two cellular capacities intimately related to physiology and pathophysiology of the cardiovascular system. Furthermore, we critically discuss the major parameters and signaling pathways that may account for the aforementioned paradoxical observations, as well as the key molecular players involved.

Effects of estrogen on growth and smooth muscle differentiation of vascular wall-resident CD34(+) stem/progenitor cells

OBJECTIVES

To investigate the effects of estrogen on growth and smooth muscle cell (SMC)-differentiation of vascular wall-resident CD34(+) stem/progenitor cells (VRS/Pcs).

METHODS AND RESULTS

The existence of CD34(+) VRS/Pcs was confirmed by immunohistochemistry in the adventitia of arteries of young (2-month-old) and old (24-month-old) female SD rats with less CD34(+) adventitial cells detected in the old. The VRS/Pcs isolated from young animals were grown in Stem cell growth medium or induced to differentiate into SMC with PDGF-BB in the presence or absence of 17β-estrodiol (E2). Flow cytometry, RT-qPCR and Western blot showed that E2 promoted Brdu incorporation of the CD34(+) VRS/Pcs growing in Stem cell growth medium; but when the cells were incubated in PDGF-BB, the hormone enhanced their expression of SMC marker SM22. ChIP and IP assays showed that E2 significantly promoted the binding of pELK1-SRF complex to the promoter of c-fos gene in CD34(+) VRS/Pcs growing in the Stem cell growth medium; but when the cells were stimulated with PDGF-BB, an E2-enhanced binding of myocardin-SRF to the promoter of SM22 gene was found with enhanced expression of SRC3 and its binding to myocardin. The effects of E2 above could be blocked by the estrogen receptor antagonist ICI 182,780 or inhibited by SRF-siRNA.

CONCLUSION

Estrogen has dual effects on CD34(+) VRS/Pcs. For the undifferentiated VRS/Pcs, it accelerates their proliferation by enhancing binding of pELK1-SRF complex to c-fos gene; while for the differentiating VRS/Pcs, it promotes their differentiation to SMC through a mechanism of SRC3-mediated interaction of myocardin-SRF complex with SM22 gene.

IQGAP1 modulates the proliferation and migration of vascular smooth muscle cells in response to estrogen

Vascular smooth muscle cell (VSMC) proliferation and migration has been proven to be a critical event in the development of varicosity. Variations in estrogen levels, a pathological event related to age and pregnancy, play a role in the pathogenesis of varicosity. Previous studies have reported a different response of VSMCs following estrogen stimulation. However, the exact mechanisms involved have not yet been elucidated. In the present study, we examined the responses of lesion and normal VSMCs treated with 10(-8) M 17β-estradiol (E2) for 24 h. A differential effect of exposure to E2 was observed in these cells. IQ-domain GTPase-activating protein 1 (IQGAP1), a scaffold protein, was overexpressed in the lesion VSMCs and was shown to modulate VSMC proliferation and migration in response to E2. Furthermore, the increased expression of IQGAP1 was found to be intimately associated with a high activity of estrogen receptor α (ERα), which has been implicated in the regulation of VSMC physiological function. Additionally, we found that two critical kinases, Akt and extracellular signal-regulated kinase (ERK), mediated the activation of ERα and VSMC proliferation. According to our results, we thus concluded that high levels of IQGAP1 in VSMCs regulate the physiological reaction of the cells in response to estrogen exposure, and that kinases are involved in the process by mediating ERα activation. In view of the essential role of IQGAP1 in the physiological function of VSMCs, targeting this molecule may prove to be a promising strategy for the treatment of varicosity.

The role of perivascular adipose tissue in vascular smooth muscle cell growth

Adipose tissue is the largest endocrine organ, producing various adipokines and many other substances. Almost all blood vessels are surrounded by perivascular adipose tissue (PVAT), which has not received research attention until recently. This review will discuss the paracrine actions of PVAT on the growth of underlying vascular smooth muscle cells (VSMCs). PVAT can release growth factors and inhibitors. Visfatin is the first identified growth factor derived from PVAT. Decreased adiponectin and increased tumour necrosis factor-α in PVAT play a pathological role for neointimal hyperplasia after endovascular injury. PVAT-derived angiotensin II, angiotensin 1-7, reactive oxygen species, complement component 3, NO and H(2) S have a paracrine action on VSMC contraction, endothelial or fibroblast function; however, their paracrine actions on VSMC growth remain to be directly verified. Factors such as monocyte chemoattractant protein-1, interleukin-6, interleukin-8, leptin, resistin, plasminogen activator inhibitor type-1, adrenomedullin, free fatty acids, glucocorticoids and sex hormones can be released from adipose tissue and can regulate VSMC growth. Most of them have been verified for their secretion by PVAT; however, their paracrine functions are unknown. Obesity, vascular injury, aging and infection may affect PVAT, causing adipocyte abnormality and inflammatory cell infiltration, inducing imbalance of PVAT-derived growth factors and inhibitors, leading to VSMC growth and finally resulting in development of proliferative vascular disease, including atherosclerosis, restenosis and hypertension. In the future, using cell-specific gene interventions and local treatments may provide definitive evidence for identification of key factor(s) involved in PVAT dysfunction-induced vascular disease and thus may help to develop new therapies.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Dual effects of estrogen on vascular smooth muscle cells: receptor-mediated proliferative vs. metabolite-induced pro-senescent actions

OBJECTIVE

To investigate the mechanism for the dual effects of estrogen on vascular smooth muscle cells (VSMCs).

METHODS

Cultured rat VSMCs were exposed to gradient concentrations (10(-9)-10(-5)M) of 17β-estradiol (E(2)) with or without pre-administration of a broad-spectrum CYP450 inhibitor 1-aminobenzotriazole (ABT) (10×10(-6)M) and an estrogen receptor (ER) antagonist ICI 182,780 (10(-6)M), respectively. The growth, cell cycle progression, premature senescence, estrogen metabolites, reactive oxygen species (ROS) and DNA damage of the cells were analyzed with cell counting assay, flow cytometry, Western blot, liquid chromatography-mass spectrometry and comet assay, respectively.

RESULTS

E(2) in its physiological levels from 10(-9)M to 10(-8)M had a concentration-dependent promoting effect on growth of VSMCs. However, when the concentration increased over 10(-8)M, the growth-promoting effect gradually reversed to a growth-inhibiting action. When the activity of CYP450s was blocked by ABT, the growth-promoting effect of E(2) increased and did not reverse at high concentrations. Whereas when the ERs were blocked by ICI 182,780, E(2) showed a pure growth-inhibiting effect. The E(2) metabolites 2- and 4-hydroxyestradiols accumulated with the increase of E(2) over 10(-8)M, which accompanied by increased ROS, DNA damage and cellular senescence. All of these changes were eliminated by block of CYP450s, indicating that the VSMC growth inhibition by E(2) is due to an increased production of ROS from accumulated E(2) metabolites which induces DNA damage, leading to VSMC premature senescence.

CONCLUSION

The complex effect of E(2) is due to two opposite actions: one ER-mediated and proliferative, and the other estrogen metabolite-induced and pro-senescent.

Estrogen receptor-α but not -β or GPER inhibits high glucose-induced human VSMC proliferation: potential role of ROS and ERK

CONTEXT

The decreased incidence of cardiovascular disease in premenopausal women has been attributed, at least partially, to protective effects of estrogens. However, premenopausal women with diabetes mellitus are no longer selectively protected. High-glucose (HG) conditions have previously been shown to abolish the antimitogenic effects of 17β-estradiol (E(2)) in vascular smooth muscle cells (VSMCs).

OBJECTIVE

Because E(2) mediates its action via different estrogen receptor (ER) subtypes, we hypothesized that different subtypes may have different, if not opposing, effects on HG-induced VSMC proliferation.

METHODS AND RESULTS

Treatment of human aortic VSMCs isolated from premenopausal women with the selective ERα agonist, 4,4',4'-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol, but not with E(2), the selective ERβ agonist 2,3-bis(4-hydroxyphenyl)-propionitrile, or the selective G protein-coupled ER agonist G-1 completely prevented increased HG-induced VSMC proliferation. Under these conditions, ERα activation selectively prevented increased hydrogen peroxide (H(2)O(2)) and total intracellular reactive oxygen species (ROS) production, caused up-regulation of manganese superoxide dismutase protein and activity, and inhibited prolonged ERK phosphorylation. The latter was mediated by ROS, and ROS inhibition reversed HG-induced ERK-dependent VSMC proliferation. The selective coactivation of ERβ reversed the antimitogenic and antioxidative effects of ERα as well as the up-regulation of manganese superoxide dismutase protein expression.

CONCLUSION

Selective activation of ERα is required for reducing oxidative stress and the consequent hyperproliferation of VSMCs under HG. Our results may further suggest that ERα activation inhibits HG-induced proliferation by down-regulating ROS-mediated ERK activation and may explain why antimitogenic effects of E(2) are abolished under HG. Pharmacological activation of ERα may thus have therapeutic potential for treating cardiovascular dysregulation associated with diabetes.

Proliferation and phenotypic changes of stromal cells in response to varying estrogen/androgen levels in castrated rats

It is known that human benign prostatic hyperplasia might arise from an estrogen/androgen (E/T) imbalance. We studied the response of castrated rat prostate to different ratios of circulating E/T. The castrated male Wistar rats were randomly injected with E/T at different ratios for 4 weeks. The prostates of E/T (1:100) group showed a distinct prostatic hyperplasia response by prostatic index, hematoxylin and eosin staining, and quantitative immunohistochemical analysis of alpha-smooth muscle actin (SMA). In this group, cells positive for Vimentin, non-muscle myosin heavy chain (NMMHC) and proliferating cell nuclear antigen (PCNA) increased in the stroma and epithelium. Furthermore, the mRNA levels of smooth muscle myosin heavy chain (SMMHC) and NMMHC increased. So E/T at a ratio of 1:100 can induce a stromal hyperplastic response in the prostate of castrated rats. The main change observed was an increase of smooth muscle cells, whereas some epithelial changes were also seen in the rat prostates.

Estrogen accelerates G1 to S phase transition and induces a G2/M phase-predominant apoptosis in synthetic vascular smooth muscle cells

OBJECTIVE

To investigate the mechanisms underlying the vascular-protective effects of estrogen.

METHODS

The synthetic (subcultured for 3-4 passages) rat vascular smooth muscle cells were exposed to gradient concentrations (10(-10)-10(-5) M) of 17beta-estradiol. The growth, cell cycle progression and apoptosis of the cells, and the related proteins including Cyclin D1, Cdk4, p38, Bax and Bcl-2 were analyzed in MTT, flow cytometry, ELISA or Western blot.

RESULTS

17beta-estradiol in the physiological concentrations (10(-10)-10(-8) M) promoted the smooth muscle cell growth in a concentration-dependent manner, accelerated transition of the cells from G1 to S phases, and up-regulated expressions of Cyclin D1 and Cdk4. Meanwhile, the hormone (10(-9)-10(-7) M) triggered a G2/M phase-predominant apoptosis of the cells in a concentration- and time-dependent manner, which was accompanied by increased phosphorylation of p38 and expression of Bax.

CONCLUSIONS

The effect of estrogen on the synthetic vascular smooth muscle cell is dual. It promotes proliferation of the cells by accelerating their G1/S phase transition via up-regulating Cyclin D1 and Cdk4; and on the other hand, it induces apoptosis of the proliferating cells by up-regulating Bax through p38-MAPK pathway.

Mitochondrial dysfunction in cardiovascular disease

Whereas the pathogenesis of atherosclerosis has been intensively studied and described, the underlying events that initiate cardiovascular disease are not yet fully understood. A substantial number of studies suggest that altered levels of oxidative and nitrosoxidative stress within the cardiovascular environment are essential in the development of cardiovascular disease; however, the impact of such changes on the subcellular or organellar components and their functions that are relevant to cardiovascular disease inception are less understood. In this regard, studies are beginning to show that mitochondria not only appear susceptible to damage mediated by increased oxidative and nitrosoxidative stress, but also play significant roles in the regulation of cardiovascular cell function. In addition, accumulating evidence suggests that a common theme among cardiovascular disease development and cardiovascular disease risk factors is increased mitochondrial damage and dysfunction. This review discusses aspects relating mitochondrial damage and function to cardiovascular disease risk factors and disease development.

Estrogen actions and in situ synthesis in human vascular smooth muscle cells and their correlation with atherosclerosis

Various epidemiological studies have demonstrated a relatively low incidence of cardiovascular events in premenopausal women and its marked increment after menopause. In addition, estrogens have been postulated to exert direct anti-atherogenic effects via binding to estrogen receptors (ERs) in vascular smooth muscle cells (VSMCs). However, not all postmenopausal women develop atherosclerosis despite decreased levels of serum estrogen. Therefore, it is considered important to examine the status of estrogen metabolism in situ and of ER expression in the human cardiovascular system. Estrone sulfate (E1S) is a major circulating plasma estrogen that is converted into the biologically active estrogen, estrone (E1) by steroid sulfatase (STS). E1 is also sulfated and reverted into E1S by estrogen sulfotransferase (EST). These two enzymes have recently been shown to play important roles in the in situ estrogen actions of estrogen-dependent human tissues. STS and EST, however, have not been studied in detail in the human vascular system associated with atherosclerotic changes. Therefore, the relative abundance of STS- and EST-immunoreactive protein and mRNA expression in human aorta were evaluated using immunohistochemistry and reverse transcription followed by quantitative polymerase chain reaction in addition to enzyme activity. Furthermore, we evaluated the relative abundance of messenger RNA (mRNA) of both ER subtypes (ERalpha and ERbeta) in the human aorta using reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR), as well as the immunoreactivity of both ERs in VSMCs of human atherosclerotic lesions. STS expression levels were found to be significantly higher in the VSMCs obtained from female aortas with mild atherosclerotic changes than in those with severe atherosclerotic changes and in male aortas regardless of atherosclerotic changes. EST expression levels in the VSMCs of these aortas, however, were significantly higher in female aortas with severe atherosclerotic changes and in male aortas than in female aortas with mild atherosclerotic changes. In addition, the number of ERalpha and/or ERbeta double positive cells in the neointima was higher in female aortas with a mild degree of atherosclerosis than in female aortas with severe atherosclerosis. They indicate that both abundance of these estrogen-metabolizing enzymes in female aorta and relative levels of ER in VSMCs of female neointima may be associated with the status of atherosclerotic changes.

Estrogen receptors in atherosclerotic human aorta: inhibition of human vascular smooth muscle cell proliferation by estrogens

Estrogen has been postulated to exert direct anti-atherogenic effects via binding to estrogen receptors (ERs) in vascular smooth muscle cells (VSMCs). Therefore, we believe it is important to examine the status of ER expression in the human cardiovascular system and its disorders. In this study, we first evaluated the relative abundance of messenger RNA (mRNA) of both ER subtypes (ERalpha and ERbeta) in the human aorta using reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR). We then examined the immunolocalization of both ERs in VSMCs of human atherosclerotic lesions. In order to examine which ER subtype was associated with the anti-atherogenic effects of estrogen, we examined the effects of estrogen in two VSMC cell lines, one positive only for ERalpha and the other positive only for ERbeta. The relative abundance of mRNAs for both ERs was higher in female aorta with a mild degree of atherosclerosis than in female aorta with a severe degree of atherosclerosis (P < 0.05). In addition, the number of ERalpha and/or ERbeta double positive cells in the neointima was higher in female aorta with a mild degree of atherosclerosis than in female aorta with severe atherosclerosis (P < 0.05). Our in vitro study found that estradiol was able to significantly inhibit the proliferation of ERalpha positive VSMCs but not ERbeta positive VSMCs (P < 0.05). Moreover, estradiol was found to significantly suppress proliferating cell nuclear antigen (PCNA) mRNA levels in ERalpha positive VSMCs compared to that of ERbeta positive VSMCs, consistent with the findings of cell proliferation. Results from this study suggest that estrogens can inhibit the proliferation of VSMCs through ERalpha, especially in pre-menopausal women. Our study also indicates that decreased levels of ER, especially ERalpha, in the female atherosclerotic neointima may be associated with progression of atherosclerotic changes.

Cholesterol-fed ovariectomized monkeys are good animal models for human atherosclerosis of postmenopausal women

Although it is well known that the incidence of atherosclerosis is markedly increased in postmenopausal women, antiatherosclerotic effects of estrogen replacement therapies are not clear. One of the reasons for this is due to the lack of appropriate animal models for atherosclerosis of postmenopausal women. Therefore, we attempted to develop an animal model for atherosclerosis of postmenopausal women and examined the antiatherosclerotic effects of estrogen replacement therapy. Adult ovariectomized Japanese monkeys were fed 2% cholesterol diet alone (C-group) or in combination with conjugated estrogen (CE-group) for 30 months. The serum estradiol-17beta levels of the CE-group were varied between 10 and 204.5 ng/dl during treatment. In the C-group, the serum total cholesterol levels were increased from 110 to 270 mg/dl, and atheroma was first observed after 3-months treatment with angioscopy. In the CE-group, the levels of the serum total cholesterol during treatment were 30% lower than those of the C-group, and the aortic lesions were first observed after 12-months treatment with angioscopy. The aortic intimal thickness of the CE-group was 58% of the C-group. This finding showed good agreement with the angioscopic observation. The aortic lesions were of a fibromuscular type in both groups. In conclusion, a cholesterol-fed ovariectomized monkey is an appropriate animal model for atherosclerosis of postmenopausal women. Furthermore, angiofiberscopic and histopathological observations suggested that estrogen replacement therapy was valid for atherosclerosis of postmenopausal women.

Role of estrogen in the regulation of cholesteryl ester synthesis in macrophages: the interaction between native and modified low density lipoprotein and human monocyte-derived macrophages

OBJECTIVES

To study the effects of estrogen on the changes in cholesterol esterification induced by native and modified low density lipoprotein (LDL) in macrophages.

DESIGN AND METHODS

Human monocyte-derived macrophages (HMDM) were used, and the influence of the presence of 17beta estradiol in the short term, and during the maturation of the cells, on the esterification of cholesterol from native (nLDL), acetylated (acLDL) and oxidized (oxLDL) LDL was determined.

RESULTS

In the short-term (6 h), 17beta estradiol (1.5 x 10(-6)M) did not affect the esterification of cholesterol from acLDL or oxLDL, but with native LDL (nLDL) a 1.5-fold increase was observed. In contrast, long-term exposure of HMDM during maturation to 17beta-estradiol (1.5 x 10(-9)M - 1.5 x 10(-5)M) decreased cholesterol esterification in the presence of oxLDL and acLDL, but not nLDL.

CONCLUSIONS

These results suggest that both the time of exposure and the concentration of estrogen used influence its effects on the interaction between HMDM and LDL, and thus on macrophage foam cell formation.

Estrogen regulation of endothelial and smooth muscle cell migration and proliferation: role of p38 and p42/44 mitogen-activated protein kinase

OBJECTIVE

Restenosis is a major limitation of percutaneous coronary intervention. Migration and proliferation of vascular cells remain a cornerstone in neointimal formation. The cardioprotection of estrogen is well recognized, but the intracellular mechanisms related to these beneficial effects are not completely understood.

METHODS AND RESULTS

We investigated the effects of 17beta-estradiol (17betaE) on mitogen-activated protein kinase (MAPK) activity and the migration and proliferation of porcine aortic endothelial cells (PAECs) and porcine smooth muscle cells (PSMCs). Treatment with 17betaE (10(-8) mol/L) abrogated p38 and p42/44 MAPK phosphorylation mediated by platelet-derived growth factor-BB as well as the migration and proliferation of PSMCs. In contrast, treatment with 17betaE (10(-8) mol/L) induced the phosphorylation of p38 and p42/44 MAPK and the migration and proliferation of PAECs. Interestingly, the effects of 17betaE on PSMCs and PAECs were reversed by selective estrogen receptor antagonists (tamoxifen, 4-OH-tamoxifen, and raloxifen). These results suggest that in PSMCs, 17betaE inhibits chemotactic and mitogenic effects of platelet-derived growth factor-BB as well as p38 and p42/44 MAPK phosphorylation. In contrast, 17betaE promotes in PAECs the phosphorylation of p42/44 and p38 MAPK as well as the migration and proliferation of these cells.

CONCLUSIONS

Treatment with 17betaE has a dual beneficial effect: the improvement of vascular healing and the prevention of restenosis after angioplasty.

Regional differences in the extracellular matrix of the human spongy urethra as evidenced by the composition of glycosaminoglycans

PURPOSE

Despite the concept that the spongy urethra is a unique entity clinical evidence suggests the existence of segmental structural differences. The spongy urethra has a vascular nature, its cells may express different phenotypes and the extracellular matrix that they synthesize should reflect these differences. Glycosaminoglycans are components of the extracellular matrix that have key roles in the normal physiology and pathology of several tissues. Although total collagen content of the urethra was determined, we also analyzed urethral glycosaminoglycans (GAGs).

MATERIALS AND METHODS

Fresh, macroscopically normal cadaveric urethral samples were obtained from 15 men who died at a mean age of 25.4 years. The urethra was divided into glanular, penile and bulbar segments, which were then analyzed separately. Total GAG concentration was assessed by hexuronic acid assay and expressed as microg. hexuronic acid per mg. dry tissue, while the proportions of sulfated GAGs were determined by agarose gel electrophoresis. Hyaluronan concentration was determined by ion exchange chromatography and total tissue collagen was estimated as hydroxyproline content.

RESULTS

Total GAG concentration was heterogeneous along the spongy urethra (p <0.001). Mean values plus or minus standard deviation in the glanular, penile and bulbar segments were 2.53 +/- 0.42, 2.11 +/- 0.47 and 1.47 +/- 0.4 microg./mg., respectively. The most predominant GAG was hyaluronan and its highest mean concentration of 50.1% +/- 3.7% was found in the glanular urethra. The most predominant sulfated GAG in the male urethra was dermatan sulfate, followed by chondroitin sulfate and heparan sulfate. Total collagen content and the GAG-to-collagen ratio varied along the spongy urethra and were lowest in the bulbar segment.

CONCLUSIONS

The extracellular matrix of the human spongy urethra shows regional differences, as evidenced by biochemical analysis of GAG and collagen. This heterogeneity implies functional adaptations in the various segments and may affect the physiology and segmental incidence of urethral diseases.

High glucose abolishes the antiproliferative effect of 17beta-estradiol in human vascular smooth muscle cells

We examined effects of 17beta-estradiol (E(2)) on human vascular smooth muscle cell (VSMC) proliferation under normal (5 mmol/l) and high (25 mmol/l) glucose concentrations. Platelet-derived growth factor (PDGF) BB (20 ng/ml)-induced increases in DNA synthesis and proliferation were greater in high than normal glucose concentrations; the difference in DNA synthesis was abolished by a protein kinase C (PKC)-beta inhibitor, LY-379196 (30 nmol/l). Western blotting showed that PKC-beta(1) protein increased in cells exposed to high glucose, whereas PKC-alpha protein and total PKC activity remained unchanged, compared with normal glucose cultures. In normal glucose, E(2) (1-100 nmol/l) inhibited PDGF-induced DNA synthesis by 18-37% and cell proliferation by 16-22% in a concentration-dependent manner. The effects of E(2) were blocked by the estrogen receptor (ER) antagonist ICI-182780, indicating ER dependence. In high glucose, the inhibitory effect of E(2) on VSMC proliferation was abolished but was restored in the presence of the PKC-beta inhibitor LY-379196. Thus high glucose enhances human VSMC proliferation and attenuates the antiproliferative effect of E(2) in VSMC via activation of PKC-beta.

Osteopontin gene expression and immunolocalization in the rabbit urinary tract

PURPOSE

Osteopontin is a highly phosphorylated, calcium binding sialoprotein characterized by a conserved arginine-glycine-aspartate sequence. Vitronectin receptor (alphavbeta3 integrin) and hyaluronan receptor (CD44) are documented as receptors for osteopontin and their expression has been established in the bladder. Based on that finding and the fact that osteopontin protein is present in urine we hypothesized that osteopontin is expressed in the lower urinary tract.

MATERIALS AND METHODS

Osteopontin messenger (m)RNA and protein were analyzed in 5 adult urinary tracts and 5 neonatal bladders of New Zealand White rabbits using reverse transcriptase-polymerase chain reaction and immunohistochemical testing. Analysis of mRNA expression and localization of osteopontin receptors, alphavbeta3 integrin and CD44 were also performed in adult bladders and primary cultures of detrusor myocytes.

RESULTS

Adult renal pelvis, ureter, bladder and urethra, and neonatal bladders contained significant levels of osteopontin mRNA. Immunohistochemical staining revealed osteopontin expression in all layers of the transitional epithelium of the bladder, co-localizing with alphavbeta3 integrin mainly in the superficial layers and with CD44 mainly in the basal layers. Osteopontin was detected within the cytoplasm of smooth muscle cells, while alphavbeta3 integrin was located closer to the plasmalemma. Furthermore, primary cultured detrusor myocytes expressed osteopontin mRNA in stable fashion for up to 4 passages. Treating bladder myocyte cultures with insulin-like growth factor-1 and 17beta-estradiol resulted in up-regulation and down-regulation of osteopontin mRNA, respectively.

CONCLUSIONS

Adult and neonatal rabbit detrusors are a prominent source of osteopontin in vivo and in vitro. Epithelial osteopontin may be a source of osteopontin in urine. The co-localization of osteopontin in the bladder epithelium with alphavbeta3 integrin and CD44 suggests a role in maintaining the integrity of the transitional epithelium by providing the sealing and adhesiveness needed for the impermeable state of the bladder.

Inhibition of MEK1,2/ERK mitogenic pathway by estrogen with antiproliferative properties in rat aortic smooth muscle cells

Proliferation and migration of vascular smooth muscle cells (VSMCs) are believed to contribute significantly to intimal thickening in atheroscleosis, restenosis, and venous bypass graft disease. Estrogen inhibits proliferation and migration of VSMCs. However, antiproliferative mechanisms of estrogen were not well elucidated yet. In this study, we investigated the antiproliferative effect of estrogen to determine whether the transduction signals and protooncogenes were affected in rat aortic smooth muscle cells (RASMCs). Estrogen inhibited the proliferative response stimulated by 5% fetal bovine serum (FBS) dose-dependently in RASMCs (IC50: 40 nM). In 0.5% serum-treated RASMCs, estrogen dramatically inhibited the activity of extracellular signal-regulated kinases (ERK) followed by inhibition of MEK1,2 activity in dose-dependent manner without affecting the other mitogen-activating protein kinases (MAPKs), c-jun N-terminal kinases (JNK) and p38. Induction of Elk-1 mRNA was significantly reduced dose-dependently up to 100 nM of estrogen. These results indicate that the antiproliferative effects of estrogen in RASMCs involved ERK inhibition followed by the inactivation of MEK1,2 and downregulation of Elk-1 expression.

An estimate of rapid cytoplasmic calcium buffering in a single smooth muscle cell

Cytoplasmic calcium increments in the absence of sarco (endo) plasmic reticulum function were measured with a low-affinity fluorophore Indo-1FF in single isolated smooth muscle cells from guinea-pig urinary bladder. To evaluate the Ca(2+)-buffering properties of the myoplasm, Ca2+ influx, measured as time integral of the Ica (integral of Ica), was compared with corresponding free Ca2+ increments (delta [Ca2+]i) in the cytoplasm. The ratio between integral of ICa and delta [Ca2+]i (integral Ica/delta [Ca2+]i), reflecting the Ca2+ buffering properties of the cytosol, was in the range of 4.9-9.3 pC/microM (mean 6.2 +/- 1.2, n = 12). It remained approximately constant (6.4 +/- 1.4 pC/microM, n = 8) during recordings lasting up to 25 min, suggesting that cytoplasmic Ca2+ binding does not change markedly during cell dialysis and that the endogenous Ca2+ buffer is not significantly washed out of the cell through the patch pipette. Wash-in or wash-out of BAPTA, a mobile high-affinity Ca2+ buffer, into or from the cell markedly changed the relationship between Ca2+ influx through Ca2+ channels and delta [Ca2+]i within minutes. Changes in integral of ICa/delta [Ca2+]i during the sequence of depolarizing steps, which increased free [Ca2+]i up to 5 microM, suggested lower limits for the apparent affinity of a rapid Ca2+ buffer (16 microM) and for the total buffer concentration (530 microM). Introduction of 4 mM DPTA (Kd for Ca2+ = 81 microM) into the cell more than doubled the total cytoplasmic Ca2+ buffer capacity. These results suggest that cytoplasmic Ca2+ buffer in smooth muscle cells has a low affinity for free Ca2+. The Ca(2+)-binding ratio of the cytoplasm in most cells was estimated to be between 30 and 40. The Ca(2+)-binding ratio did not differ markedly between cells isolated from neonatal (< or = 5 days) and adult animals.

Smooth muscle cell phenotypes in atherosclerotic lesions

Recently, there has been a dramatic change in the way we think about the role of vascular smooth muscle cells in atherosclerosis, and it is now generally accepted that a dearth of vascular smooth muscle cells in an atherosclerotic plaque is a detrimental feature of the disease. Indeed, it is now recognized that the phenotypes of vascular smooth muscle cells within a plaque dictate its features, progression and stability. Therefore an understanding of the processes that generate and regulate vascular smooth muscle cell heterogeneity are of critical importance for future therapeutic advancement in the treatment of atherosclerosis.