Homeostasis In Vascular Smooth Muscle Cells Research Articles

Colchicine Blocks Abdominal Aortic Aneurysm Development by Maintaining Vascular Smooth Muscle Cell Homeostasis.

Development of non-surgical treatment of human abdominal aortic aneurysm (AAA) has clinical significance. Colchicine emerges as an effective therapeutic regimen in cardiovascular diseases. Yet, whether colchicine slows AAA growth remain controversy. Here, we demonstrated that daily intragastric administration of low-dose colchicine blocked AAA formation, prevented vascular smooth muscle cell (SMC) phenotype switching and apoptosis, and vascular inflammation in both peri-aortic CaPO4 injury and subcutaneous angiotensin-II infusion induced experimental AAA mice models. Mechanistically, colchicine increased global mRNA stability by inhibiting the METTL14/YTHDC1-mediated m6A modification, resulting in increased sclerostin (SOST) expression and consequent inactivation of the WNT/β-catenin signaling pathway in vascular SMCs from mouse AAA lesions and in cultured human aortic SMCs. Moreover, human and mouse AAA lesions all showed increased m6A methylation, decreased SOST expression, and skewed synthetic SMC de-differentiation phenotype, compared to those without AAA. This study uncovers a novel mechanism of colchicine in slowing AAA development by using the METTL14/SOST/WNT/β-catenin axis to control vascular SMC homeostasis in mouse aortic vessels and in human aortic SMCs. Therefore, use of colchicine may benefit AAA patients in clinical practice.

HRD1 reduction promotes cholesterol-induced vascular smooth muscle cell phenotypic change via endoplasmic reticulum stress.

Phenotypic change of vascular smooth muscle cells (VSMCs) is the main contributor of vascular pathological remodeling in atherosclerosis. The endoplasmic reticulum (ER) is critical for maintaining VSMC function through elimination of misfolded proteins that impair VSMC cellular function. ER-associated degradation (ERAD) is an ER-mediated process that controls protein quality by clearing misfolded proteins. One of the critical regulators of ERAD is HRD1, which also plays a vital role in lipid metabolism. However, the function of HRD1 in VSMCs of atherosclerotic vessels remains poorly understood. The level of HRD1 expression was analyzed in aortic tissues of mice fed with a high-fat diet (HFD). The H&E and EVG (VERHOEFF'S VAN GIESON) staining were used to demonstrate pathological vascular changes. IF (immunofluorescence) and WB (western blot) were used to explore the signaling pathways in vivo and in vitro. The wound closure and transwell assays were also used to test the migration rate of VSMCs. CRISPR gene editing and transcriptomic analysis were applied in vitro to explore the cellular mechanism. Our data showed significant reduction of HRD1 in aortic tissues of mice under HFD feeding. VSMC phenotypic change and HRD1 downregulation were detected by cholesterol supplement. Transcriptomic and further analysis of HRD1-KO VSMCs showed that HRD1 deficiency induced the expression of genes related to ER stress response, proliferation and migration, but reduced the contractile-related genes in VSMCs. HRD1 deficiency also exacerbated the proliferation, migration and ROS production of VSMCs induced by cholesterol, which promoted the VSMC dedifferentiation. Our results showed that HRD1 played an essential role in the contractile homeostasis of VSMCs by negatively regulating ER stress response. Thus, HRD1 in VSMCs could serve as a potential therapeutic target in metabolic disorder-induced vascular remodeling.

Alterations of the Ca2+ clearing mechanisms by type 2 diabetes in aortic smooth muscle cells of Zucker diabetic fatty rat.

Type 2 Diabetes Mellitus (T2DM) is a rapidly rising disease with cardiovascular complications constituting the most common cause of death among diabetic patients. Chronic hyperglycemia can induce vascular dysfunction through damage of the components of the vascular wall, such as vascular smooth muscle cells (VSMCs), which regulate vascular tone and contribute to vascular repair and remodeling. These functions are dependent on intracellular Ca2+ changes. The mechanisms by which T2DM affects Ca2+ handling in VSMCs still remain poorly understood. Therefore, the objective of this study was to determine whether and how T2DM affects Ca2+ homeostasis in VSMCs. We evaluated intracellular Ca2+ signaling in VSMCs from Zucker Diabetic Fatty rats using Ca2+ imaging with Fura-2/AM. Our results indicate that T2DM decreases Ca2+ release from the sarcoplasmic reticulum (SR) and increases the activity of store-operated channels (SOCs). Moreover, we were able to identify an enhancement of the activity of the main Ca2+ extrusion mechanisms (SERCA, PMCA and NCX) during the early stage of the decay of the ATP-induced Ca2+ transient. In addition, we found an increase in Ca2+ entry through the reverse mode of NCX and a decrease in SERCA and PMCA activity during the late stage of the signal decay. These effects were appreciated as a shortening of ATP-induced Ca2+ transient during the early stage of the decay, as well as an increase in the amplitude of the following plateau. Enhanced cytosolic Ca2+ activity in VSMCs could contribute to vascular dysfunction associated with T2DM.

Different effects of fenoldopam and angiotensin II on autophagy in vascular smooth muscle cells

Both dopamine and angiotensin II are essential neurotransmitters/hormones with pleiotropic functions in vascular smooth muscle cells (VSMCs). Autophagy, an intracellular self-degradative process that delivers cytoplasmic constituents to lysosomes, plays an important role in physiological homeostasis in VSMCs. Fenoldopam (Fen), a dopamine D 1 /D 5 receptor agonist, increases autophagic flux in renal proximal tubule cells, however, in VSMCs the roles of these two neurotransmitters on autophagy are unknown. In rat aortic VSMCs, Fen increased autophagy, determined by the protein expression of microtubule-associated protein 1 light chain (LC)3-II and autophagy related 5 (ATG5), in a concentration- and time-dependent manner. By contrast, angiotensin II (Ang II), the endogenous AT 1 R agonist, decreased the protein expression of LC3-II and ATG5 in a concentration-and time-dependent manner. Further studies showed that Fen (1 μM, 15 min) increased while Ang II (100 nM, 15 min) decreased cyclic AMP (cAMP) production in VSMCs (Vehicle: 100±35.4%, Fen: 513.7±95.8%, Ang II: 24.6±8.0%, n=6). Pre-treatment with Rp-cAMPS (50 μM, 6 hr), a PKA inhibitor, attenuated the Fen-mediated increase in LC3-II protein expression (Fen: 1 μM, 6 hr) (Vehicle: 100±15.0%, Fen: 251.8±37.2%, Fen+Rp-cAMP: 96.9±16.7%, n=6) and reversed the Ang II-mediated decrease in autophagy (Ang II: 100 nM, 6 hr) (Vehicle: 100±8.9%, Ang II: 44.9±6.3%, Ang II+Rp-cAMP: 95.4±11.0%, n=4). These results demonstrate distinct roles of Fen and Ang II on autophagy through regulation of cAMP/PKA signaling by their corresponding receptors in VSMCs. This study was supported by National Institutes of Health of US and National Natural Science Foundation of China. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mitochondrial Homeostasis in VSMCs as a Central Hub in Vascular Remodeling.

Vascular remodeling is a common pathological hallmark of many cardiovascular diseases. Vascular smooth muscle cells (VSMCs) are the predominant cell type lining the tunica media and play a crucial role in maintaining aortic morphology, integrity, contraction and elasticity. Their abnormal proliferation, migration, apoptosis and other activities are tightly associated with a spectrum of structural and functional alterations in blood vessels. Emerging evidence suggests that mitochondria, the energy center of VSMCs, participate in vascular remodeling through multiple mechanisms. For example, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α)-mediated mitochondrial biogenesis prevents VSMCs from proliferation and senescence. The imbalance between mitochondrial fusion and fission controls the abnormal proliferation, migration and phenotypic transformation of VSMCs. Guanosine triphosphate-hydrolyzing enzymes, including mitofusin 1 (MFN1), mitofusin 2 (MFN2), optic atrophy protein 1 (OPA1) and dynamin-related protein 1 (DRP1), are crucial for mitochondrial fusion and fission. In addition, abnormal mitophagy accelerates the senescence and apoptosis of VSMCs. PINK/Parkin and NIX/BINP3 pathways alleviate vascular remodeling by awakening mitophagy in VSMCs. Mitochondrial DNA (mtDNA) damage destroys the respiratory chain of VSMCs, resulting in excessive ROS production and decreased ATP levels, which are related to the proliferation, migration and apoptosis of VSMCs. Thus, maintaining mitochondrial homeostasis in VSMCs is a possible way to relieve pathologic vascular remodeling. This review aims to provide an overview of the role of mitochondria homeostasis in VSMCs during vascular remodeling and potential mitochondria-targeted therapies.

BAF60c prevents abdominal aortic aneurysm formation through epigenetic control of vascular smooth muscle cell homeostasis.

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease. BAF60c, a unique subunit of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex, is critical for cardiac and skeletal myogenesis, yet little is known about its function in the vasculature and, specifically, in AAA pathogenesis. Here, we found that BAF60c was downregulated in human and mouse AAA tissues, with primary staining to vascular smooth muscle cells (VSMCs), confirmed by single-cell RNA-sequencing. In vivo studies revealed that VSMC-specific knockout of Baf60c significantly aggravated both angiotensin II- (Ang II-) and elastase-induced AAA formation in mice, with a significant increase in elastin degradation, inflammatory cell infiltration, VSMC phenotypic switch, and apoptosis. In vitro studies showed that BAF60c knockdown in VSMCs resulted in loss of contractile phenotype, increased VSMC inflammation, and apoptosis. Mechanistically, we demonstrated that BAF60c preserved VSMC contractile phenotype by strengthening serum response factor (SRF) association with its coactivator P300 and the SWI/SNF complex and suppressing VSMC inflammation by promoting a repressive chromatin state of NF-κB target genes as well as preventing VSMC apoptosis through transcriptional activation of KLF5-dependent B cell lymphoma 2 (BCL2) expression. Our identification of the essential role of BAF60c in preserving VSMC homeostasis expands its therapeutic potential in preventing and treating AAA.

Nuclear receptor Nur77 protects against oxidative stress by maintaining mitochondrial homeostasis via regulating mitochondrial fission and mitophagy in smooth muscle cell

Angiotensin II (AngII) induces disruption of mitochondrial homeostasis and oxidative stress. Nuclear receptor NR4A1 (Nur77) plays an important role in vascular smooth muscle cells (VSMCs) function. However, the role of Nur77 in AngII-induced mitochondrial dynamics and oxidative stress in VSMCs remains unknown. In an in vitro model of AngII-treated cells, we discovered that Nur77 knockout aggravated AngII-induced oxidative stress in VSMCs, whereas activation of Nur77 by celastrol diminished them. Concomitantly, disturbance of mitochondrial dynamics induced by AngII was further exacerbated in Nur77 deficient VSMCs compared to wild-type (WT) VSMCs. Interestingly, Nur77 deletion increased mitochondrial fission but not fusion as evidenced by upregulated fission related genes (Fis1 and Drp1) but not fusion (Opa1 and Mfn2) under AngII stimulation in VSMCs. Mechanically, Nur77 could directly bind to the promoter regions of Fis1 and Drp1 and repress their transcription. Furthermore, we observed that Nur77 additionally promoted mitochondrial homeostasis by increasing mitophagic flux in a transcription-independent manner upon AngII challenge. By using an in vivo model of AngII-induced abdominal aortic aneurysm (AAA), we finally validated the protective role of Nur77 involved in the mitochondrial fission process and mitophagic flux in aortas, which was correlated with the occurrence and development of AAA in AngII-infused mice. Our data defines an essential role of Nur77 in regulating oxidative stress by maintaining mitochondrial homeostasis in VSMCs via both transcription-dependent and transcription-independent manner, supporting the therapeutic potential of Nur77 targeting in vascular diseases.

Role of mitochondrial dynamics and mitophagy of vascular smooth muscle cell proliferation and migration in progression of atherosclerosis.

Vascular smooth muscle cell (VSMC) proliferation and migration are critical events that contribute to the pathogenesis of vascular diseases such as atherosclerosis, restenosis, and hypertension. Recent findings have revealed that VSMC phenotype switching is associated with metabolic switch, which is related to the role of mitochondria. Mitochondrial dynamics are directly associated with mitochondrial function and cellular homeostasis. Interestingly, it has been suggested that mitochondrial dynamics and mitophagy play crucial roles in the regulation of VSMC proliferation and migration through various mechanisms. Especially, dynamin-related protein-1 and mitofusion-2 are two main molecules that play a key role in regulating mitochondrial dynamics to induce VSMC proliferation and migration. Therefore, this review describes the function and role of mitochondrial dynamics and mitophagy in VSMC homeostasis as well as the underlying mechanisms. This will provide insight into the development of innovative approaches to treat atherosclerosis.

Abstract 129: BAF60c Prevents Abdominal Aortic Aneurysm Formation Through Maintaining Vascular Smooth Muscle Cell Homeostasis

Background: Abdominal aortic aneurysm (AAA) is a common and life-threatening vascular disease. Vascular smooth muscle cell (VSMC) dysfunction is involved in the dilatation and eventual rupture of AAA, with the precise epigenetic control of this process less studied. BAF60c, a unique subunit of SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex, serves as a core modulator of physiological and pathological processes, yet little is known about its function in the vasculature and pathogenesis of AAA. Methods and Results: BAF60c is downregulated in AAAs from humans and mice with primary staining to the aortic VSMC, confirmed by single cell RNA sequencing. In vivo studies revealed that VSMC-specific knockout Baf60c markedly aggravated both AngII- and elastase-induced murine AAA formation, with significant increases of elastin degradation, inflammatory cell accumulation, VSMC phenotype switching, and apoptosis. In vitro studies showed that knockdown of BAF60c in human aortic smooth muscle cells resulted in the loss of contractile phenotype while upregulation of inflammatory genes and increased apoptosis. Chromatin immunoprecipitation followed by sequencing and qPCR, as well as CoIP assays showed that BAF60c maintained VSMC contractile phenotype by enhancing serum response factor association with its co-activator p300 and SWI/SNF complex, suppressed VSMC inflammation via precise control of the repressive state of NF-κB-target genes, as well as prevented VSMC apoptosis through transcriptional activation of KLF5-dependent BCL2 expression. Conclusions: Our study indicates that BAF60c is essential for SWI/SNF complex recruitment to chromatin and interaction with diverse transcription factors to precise epigenetic control of VSMC homeostasis and prevention of AAA formation.

Loss of FoxO3a prevents aortic aneurysm formation through maintenance of VSMC homeostasis

Vascular smooth muscle cell (VSMC) phenotypic switching plays a critical role in the formation of abdominal aortic aneurysms (AAAs). FoxO3a is a key suppressor of VSMC homeostasis. We found that in human and animal AAA tissues, FoxO3a was upregulated, SM22α and α-smooth muscle actin (α-SMA) proteins were downregulated and synthetic phenotypic markers were upregulated, indicating that VSMC phenotypic switching occurred in these diseased tissues. In addition, in cultured VSMCs, significant enhancement of FoxO3a expression was found during angiotensin II (Ang II)-induced VSMC phenotypic switching. In vivo, FoxO3a overexpression in C57BL/6J mice treated with Ang II increased the formation of AAAs, whereas FoxO3a knockdown exerted an inhibitory effect on AAA formation in ApoE−/− mice infused with Ang II. Mechanistically, FoxO3a overexpression significantly inhibited the expression of differentiated smooth muscle cell (SMC) markers, activated autophagy, the essential repressor of VSMC homeostasis, and promoted AAA formation. Our study revealed that FoxO3a promotes VSMC phenotypic switching to accelerate AAA formation through the P62/LC3BII autophagy signaling pathway and that therapeutic approaches that decrease FoxO3a expression may prevent AAA formation.

Analysis of Vascular Cell Response to Hypertension Induced by Pressure Loading and Its Application as a Tool for Exploring Pharmacological Modes of Action.

Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression is induced by interleukin-1β (IL-1β) stimulation in vascular smooth muscle cells (VSMCs), resulting in the production of nitric oxide and prostaglandins such as PGI2. The expression of iNOS and COX-2 in cultured VSMCs isolated from 6-7-week-old stroke-prone spontaneously hypertensive rats (SHRSP) is significantly lower than in cells of normotensive Wistar Kyoto rats (WKY). These reductions are also found in cells exposed to pulsatile atmospheric pressure between 80-160 mmHg at a rate of 4 cycles/min, which simulates systolic hypertension. Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, potentiates IL-1β-induced iNOS and COX-2 expression in VSMCs isolated from WKY, but not those from SHRSP. In response to endothelial injury at a local site, iNOS and COX-2 induction in VSMCs may function primarily as a defensive and compensatory mechanism for endothelial dysfunction by preventing the development of pathological conditions. Thus, in certain pathological conditions associated with hypertension, vascular walls with reduced iNOS and COX-2 expression may aggravate or initiate further vascular injury. In this situation, DHA may contribute to maintaining homeostasis in VSMCs by potentiating iNOS and COX-2 expression. Using cells isolated from a genetic pathological animal model alongside cells exposed to experimental pathological conditions can be an effective tool for the analysis of cell response to hypertension and exploring pharmacological modes of action in vitro.

MicroRNA regulation of vascular smooth muscle function and phenotype: early career committee contribution.

In periods of health, the vascular smooth muscle cell (VSMC) predominantly functions to regulate vascular tone and to provide structural integrity to the vascular tree. However, the VSMC is also one of the most plastic cells in the body. Under periods of stress, or in response to disease stimuli, the VSMC deviates from its physiologic state and can become hyperproliferative, migratory and/or proinflammatory. Such de-differentiation is believed to contribute to a variety of maladaptive processes with relevance to vascular disease, including de novo atherogenesis, postangioplasty neointimal hyperplasia, aneurysmal degeneration, medial calcinosis, and even foam cell formation. In an effort to modulate these conditions, scientists have sought the master regulators of VSMC physiology and plasticity, and have made progress identifying a number of transcriptional cofactors that modulate expression of the contractile apparatus and genes which are activated in the perturbed VSMC. Recent work, however, has shown that several epigenetic factors also modify VSMC behavior and could similarly serve as translational targets or biomarkers of disease. In the review provided below, we will focus on the role of microRNAs as the best studied of these factors, and provide an overview of their important role in VSMC homeostasis and pathophysiology. In the nondiseased artery, the tunica media is comprised almost exclusively of VSMCs and the connective tissues secreted by these cells. The VSMC serves to modulate vascular tone, and therefore, end-organ perfusion, by contracting and relaxing in response to sympathetic innervation and diffusible factors, such as nitric oxide released from the overlying endothelial cells of the tunica intima.1–3 Their related extracellular matrix proteins comprise the scaffolding, which provide the structural support necessary to withstand the radial force applied to the vessel during the cardiac cycle. At the molecular level, the VSMC is dominated …

Effects of Magnesium Lithospermate B and its Analogues on Ca2+Homeostasis in Cultured Rat Thoracic Aorta Vascular Smooth Muscle Cells

Magnesium lithospermate B (MLB), sodium rosmarinate (SR), and magnesium lithospermate (ML) are biologically active components isolated from aqueous extracts of the Chinese medicine Danshen, the dried root and rhizome of SALVIA MILTIORRHIZA Bunge (Labiatae). These compounds share similar chemical structures of polyphenols and oligomer condensates with caffeic acid. In this study, we compared the effects of MLB, ML, and SR on intracellular Ca (2+) concentrations ([Ca (2+)] (i)) in cultured rat thoracic aorta vascular smooth muscle cells (VSMCs), using the Ca (2+)-sensitive dye, Fluo-3, as an indicator. In our experiments, MLB, ML, and SR did not affect the basal value of [Ca (2+)] (i) in VSMCs. In the absence of extracellular Ca (2+), the [Ca (2+)] (i) increase in VSMCs induced by 20 microM ATP was attenuated by MLB, ML, and SR in a dose-dependent manner. Moreover, under this condition, MLB suppressed the increase in [Ca (2+)] (i) in VSMCs induced by 1 microM thapsigargin, but not ML or SR. In the presence of extracellular Ca (2+), the [Ca (2+)] (i) increase in VSMCs induced by 60 mM KCl was attenuated by MLB and SR in a dose-dependent manner, but not by ML. These results suggest that MLB, ML and SR regulate Ca (2+) homeostasis in VSMCs via different pathways. Our findings should aid in elucidating the mechanisms of the vasodilator action of aqueous extracts of SALVIA MILTIORRHIZA.

Hypoxia regulates resistin in vascular smooth muscle cells, what next?

Hypoxia regulates resistin in vascular smooth muscle cells, what next?

Control of Phenotypic Plasticity of Smooth Muscle Cells by Bone Morphogenetic Protein Signaling through the Myocardin-related Transcription Factors

Vascular smooth muscle cells (VSMCs), unlike other muscle cells, do not terminally differentiate. In response to injury, VSMCs change phenotype, proliferate, and migrate as part of the repair process. Dysregulation of this plasticity program contributes to the pathogenesis of several vascular disorders, such as atherosclerosis, restenosis, and hypertension. The discovery of mutations in the gene encoding BMPRII, the type II subunit of the receptor for bone morphogenetic proteins (BMPs), in patients with pulmonary arterial hypertension (PAH) provided an indication that BMP signaling may affect the homeostasis of VSMCs and their phenotype modulation. Here we report that BMP signaling potently induces SMC-specific genes in pluripotent cells and prevents dedifferentiation of arterial SMCs. The BMP-induced phenotype switch requires intact RhoA/ROCK signaling but is not blocked by inhibitors of the TGFbeta and PI3K/Akt pathways. Furthermore, nuclear localization and recruitment of the myocardin-related transcription factors (MRTF-A and MRTF-B) to a smooth muscle alpha-actin promoter is observed in response to BMP treatment. Thus, BMP signaling modulates VSMC phenotype via cross-talk with the RhoA/MRTFs pathway, and may contribute to the development of the pathological characteristics observed in patients with PAH and other obliterative vascular diseases.

Differential regulation of transient receptor potential melastatin 6 and 7 cation channels by ANG II in vascular smooth muscle cells from spontaneously hypertensive rats

Intracellular Mg2+ depletion has been implicated in vascular dysfunction in hypertension. We demonstrated that transient receptor potential melastatin 7 (TRPM7) cation channels mediate Mg2+ influx in VSMCs. Whether this plays a role in [Mg2+]i deficiency in hypertension is unclear. Here, we tested the hypothesis that downregulation of TRPM7 and its homologue TRPM6 is associated with reduced [Mg2+]i and that ANG II negatively regulates TRPM6/7 in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR). Cultured VSMCs from Wistar Kyoto (WKY) and SHR were studied. mRNA and protein expression of TRPM6 and TRPM7 were assessed by RT-PCR and immunoblotting, respectively. Translocation of annexin-1, specific TRPM7 substrate, was measured as an index of TRPM7 activation. [Mg2+]i was determined using mag fura-2. VSMCs from WKY and SHR express TRPM6 and TRPM7. Basal TRPM6 expression was similar in WKY and SHR, but basal TRPM7 content was lower in VSMCs from SHR vs. WKY. This was associated with significantly reduced [Mg2+]i in SHR cells (P < 0.01). ANG II time-dependently increased TRPM6 expression, with similar responses in WKY and SHR. ANG II significantly increased TRPM7 expression in WKY (P < 0.05), but not in SHR. Annexin-1 translocation was reduced 1.5-2-fold in SHR vs. WKY. Our findings demonstrate that TRPM6 and TRPM7 are differentially regulated in VSMCs from SHR and WKY. Whereas TRPM6 is unaltered in SHR, expression of TRPM7 is blunted. This was associated with attenuated annexin-1 translocation and decreased VSMC [Mg2+]i in SHR. Downregulation of TRPM7, but not TRPM6, may play a role in altered Mg2+ homeostasis in VSMCs from SHR.

Effects of steroid hormones on vascular functions.

The purpose of this review is to present reported findings of effects of steroids on vascular function and to discuss the biological significance in vascular physiology and pathology. Steroid hormones play various roles in vascular functions through the specific receptor localized in the endothelium and underlying vascular smooth muscle cells (VSMCs). Estrogen replacement therapy in postmenopausal women is in general associated with a reduction in mortality from cardiovascular disease and the beneficial effects of estrogens are caused by modulation of lipid metabolism, expression of leukocyte adhesion molecules, and migration of VSMCs in the vascular wall. Estrogens also play a role as vasodilators through an increment in nitric oxide (NO) production in endothelium or modulation of calcium homeostasis in VSMCs. Some progestin molecules partially oppose the effects of estrogens on vascular functions, but striking differences exist among the types of molecules. Testosterone shows a vasorelaxant response, but detailed actions of androgens on vascular functions remain unknown. Glucocorticoids act on vasoconstriction through reduced prostacyclin production, increased alpha-adrenoceptor numbers, and inhibition of NO synthase, while mineralocorticoids induce hypertrophy and hyperplasia of VSMCs and perivascular fibrosis and cause peripheral vascular resistance, in addition to changes in vascular electrocyte permeability. Some rapid actions of steroids are mediated by "nongenomic" responses in vascular tissues. Recent studies have also demonstrated that steroid-producing or -metabolizing enzymes are expressed in the vascular wall, suggesting the local regulation of steroids in the vascular system. Thus, steroid hormones greatly influence vascular functions and an understanding of the mechanisms may provide new means to prevent vascular diseases.

Overexpression of SERCA2 Atpase in vascular smooth muscle cells treated with oxidized low density lipoprotein.

Oxidized low density lipoprotein (oxLDL) has been identified as a potentially important atherogenic factor. Atherosclerosis is characterized by the accumulation of lipid and calcium in the vascular wall. OxLDL plays a significant role in altering calcium homeostasis within different cell types. In our previous study, chronic treatment of vascular smooth muscle cells (VSMC) with oxLDL depressed Ca2+(i) homeostasis and altered two Ca2+ release mechanisms in these cells (IP3 and ryanodine sensitive channels). The purpose of the present study was to further define the effects of chronic treatment with oxLDL on the smooth muscle sarcoplasmic reticulum (SR) Ca2+ pump. One of the primary Ca2+ uptake mechanisms in VSMC is through the SERCA2 ATPase calcium pump in the sarcoplasmic reticulum. VSMC were chronically treated with 0.005-0.1 mg/ml oxLDL for up to 6 days in culture. Cells treated with oxLDL showed a significant increase in the total SERCA2 ATPase content. These changes were observed on both Western blot and immunocytochemical analysis. This increase in SERCA2 ATPase is in striking contrast to a significant decrease in the density of IP3 and ryanodine receptors in VSMC as the result of chronic treatment with oxLDL. This response may suggest a specific adaptive mechanism that the pump undergoes to attempt to maintain Ca2+ homeostasis in VSMC chronically exposed to atherogenic oxLDL.