Apoptosis in atherosclerosis: pathological and pharmacological implications

UGP2, a novel target gene of TP53, inhibits endothelial cells apoptosis and atherosclerosis

The dysfunction of the endothelial lining in lesion-prone areas of the arterial vasculature significantly contributes to the pathobiology of atherosclerotic cardiovascular disease. Recent studies suggested that UDP-glucose pyrophosphorylase 2 (UGP2) plays a role in cell proliferation and survival. This study investigates the anti-apoptotic and anti-atherogenic effects of UGP2 both in vitro and in vivo. We explored the effects and mechanisms of UGP2 on apoptosis in endothelial cells using flow cytometry and Western blot analysis. Additionally, we evaluate apoptosis levels in atherosclerotic lesions with ldlr-/- ugp2+/- mice. Microarray analysis revealed reduced UGP2 expression in human atherosclerotic plaques. In vitro experiments demonstrated that TP53 interacts with the promoter region of the UGP2 gene, upregulating UGP2 expression. Enhanced UGP2 expression led to decreased reactive oxygen species (ROS) levels, reduced Cleaved caspase-3 expression, and lower apoptosis levels in endothelial cells. The anti-apoptotic effects of UGP2 were significantly diminished by H2O2. In vivo, UGP2 deficiency in ldlr-/- mice fed a Western high-fat diet promoted atherosclerosis, increased ROS levels, and elevated Cleaved caspase-3 expression and apoptosis in atherosclerotic lesions. Our findings identify UGP2 as a novel TP53 target gene that contributes to anti-apoptotic effects by regulating ROS homeostasis via a non-canonical pathway. UGP2 represents a potential therapeutic target for ameliorating atherosclerosis-related diseases.

Effect of Akt activation on apoptosis-related gene expression in the crop tissues of male and female pigeons (Columba livia)

The current study investigated whether the expression of apoptosis genes in the pigeon crops was affected by the Akt signaling pathway during crop milk formation. First, 78 pairs of adult White King pigeons were randomly assigned to 7 groups, and the expression of apoptosis-related genes and Akt signaling pathway-related proteins in the crop tissues during different breeding stages were examined. The results showed that the mRNA levels of Bak, caspase-3, caspase-6, and caspase-9 in female crops all increased and reached their highest levels at d 17 of incubation (I17). In male crops, the levels of caspase-3 and caspase-9 gene expression peaked at d 1 of chick rearing (R1). The lowest level of Bcl-2 gene expression in females was observed at I17. The expression ratios of p-Akt (Ser473)/Akt and p-Akt (Thr308)/Akt in male crops decreased to their minimum at R1, while it was observed at d 7 of chick rearing (R7) in females. Second, 36 pairs of adult pigeons were divided into 3 groups and were subjected to SC79 injections with dosages of 0, 0.02, or 0.04 mg/kg bodyweight. The SC79 injections resulted in a considerable decrease in growth performance of pigeon squabs. In male crops, the expression ratios of p-Akt (Ser473)/Akt and p-Akt (Thr308)/Akt were significantly elevated in the 0.02 mg/kg SC79 group, while in female crops, they were higher in the 0.04 mg/kg SC79 group (P < 0.05). The SC79 injection inhibited the gene expression of Bak in female crops, but enhanced the gene expression of Bcl-2 in both male and female crops. In the 0.04 mg/kg SC79 group, a 50.7 to 75.7% decrease was observed in the expression of caspase-3, caspase-6, and caspase-9 in male and female pigeon crops. Expression of the caspase-8 gene and total Akt protein in pigeon crops was not changed in different breeding stages or after SC79 injection. In conclusion, the expression of genes related to mitochondria-dependent apoptosis can be regulated by the Akt signaling pathway, which may play a potential role in pigeon milk formation.

Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) accelerates vascular remodelling via p53 and JAK2-STAT3 regulation in vascular smooth muscle cells

BACKGROUND AND PURPOSE

Abnormal vascular smooth muscle cell (VSMC) proliferation and migration lead to neointima formation, which eventually results in cardiovascular hyperplastic diseases. The molecular mechanisms underlying these cellular processes have not been fully understood. Cytokine-induced apoptosis inhibitor 1 (CIAPIN1) has been identified as an anti-apoptotic molecule, but little is known about its target genes and related pathways in VSMC dysfunction or its clinical implication in neointima formation following vascular injury.

EXPERIMENTAL APPROACH

Determination, using loss/gain-of-function approaches by gene delivery, of whether CIAPIN1 modulates VSMC proliferation, migration and neointima formation and the underlying mechanisms was carried out. Balloon injury or ligation and local delivery of lentivirus were performed on rat or mouse carotid arteries. Rat aortic smooth muscle cells, the primary cell, was used as the model to evaluate the effect of CIAPIN1 on proliferation and migration.

KEY RESULTS

CIAPIN1 was overexpressed in the neointimal region of rat arteries. CIAPIN1 deficiency markedly inhibited injury-induced or ligation-induced intimal hyperplasia and suppressed PDGF-BB-induced VSMC proliferation, migration and cell cycle progression, while overexpression promoted proliferation, migration and neointima formation. CIAPIN1 negatively regulated Tp53 transcription, which promoted cell cycle progression and migration via cyclin E1-CDK2/pRb/PCNA and the MMP2 pathway. CIAPIN1 also increased JAK2 expression, enhancing JAK2 and STAT3 phosphorylation by vascular injury, which forced phenotypic switching from contractile to synthetic state in injured arteries.

CONCLUSIONS AND IMPLICATIONS

These findings provide new insights into the mechanism by which CIAPIN1 regulates vascular remodelling and suggest a novel therapeutic target for treating vascular proliferative diseases.

Effects of p53-knockout in vascular smooth muscle cells on atherosclerosis in mice

In vitro and in vivo evidence has indicated that the tumor suppressor, p53, may play a significant role in the regulation of atherosclerotic plaque formation. In vivo studies using global knockout mice models, however, have generated inconclusive results that do not address the roles of p53 in various cell types involved in atherosclerosis. In this study, we have specifically ablated p53 in vascular smooth muscle cells (VSMC) in the ApoE^-/- mouse model to investigate the roles of p53 in VSMC in atherosclerotic plaque formation and stability. We found that p53 deficiency in VSMC alone did not affect the overall size of atherosclerotic lesions. However, there was a significant increase in the number of p53^-/- VSMC in the fibrous caps of atherosclerotic plaques in the early stages of plaque development. Loss of p53 results in migration of VSMC at a faster rate using wound healing assays and augments PDGF-induced formation of circular dorsal ruffles (CDR), known to be involved in cell migration and internalization of surface receptors. Furthermore, aortic VSMC from ApoE^-/- /p53^-/- mice produce significantly more podosomes and are more invasive. We conclude that p53^-/- VSMC are enriched in the fibrous caps of lesions at early stages of plaque formation, which is caused in part by an increase in VSMC migration and invasion as shown by p53^-/- VSMC in culture having significantly higher rates of migration and producing more CDRs and invasive podosomes.

TGF-β1 and TIMP1 double directional rAAV targeted by UTMD in atherosclerotic vulnerable plaque

In the present study, we determined whether ultrasound-targeted microbubble destruction (UTMD) combined with dual targeting of transforming growth factor (TGF)-β1 and tissue inhibitors of metalloproteinase (TIMP) 1 recombinant adeno-associated virus (rAAV) can stabilize atherosclerotic vulnerable plaques. First, we used rabbit model to detect the TGF-β1/TIMP1 virus therapy result. H&E staining was used to evaluate the tissues. The protein levels of TGF-β1 and TIMP1 were detected in rabbit models. The THP-1 cells were induced into macrophages, and transfected with TGF-β1 and TIMP1 rAAV under optimized UTMD. The expression of TGF-β1 and TIMP1 was measured by RT-PCR and western blotting. We found that the apoptotic rates were induced when compared to the control group. The rAAV virus group showed a significant decrease in the p-ERT and p-AKT expression. These data support the hypothesis that TGF-β1 and TIMP1 are crucial in the regulation of atherosclerotic plaques.

Low-density lipoprotein electronegativity is a novel cardiometabolic risk factor

BACKGROUND

Low-density lipoprotein (LDL) plays a central role in cardiovascular disease (CVD) development. In LDL chromatographically resolved according to charge, the most electronegative subfraction-L5-is the only subfraction that induces atherogenic responses in cultured vascular cells. Furthermore, increasing evidence has shown that plasma L5 levels are elevated in individuals with high cardiovascular risk. We hypothesized that LDL electronegativity is a novel index for predicting CVD.

METHODS

In 30 asymptomatic individuals with metabolic syndrome (MetS) and 27 healthy control subjects, we examined correlations between plasma L5 levels and the number of MetS criteria fulfilled, CVD risk factors, and CVD risk according to the Framingham risk score.

RESULTS

L5 levels were significantly higher in MetS subjects than in control subjects (21.9±18.7 mg/dL vs. 11.2±10.7 mg/dL, P:0.01). The Jonckheere trend test revealed that the percent L5 of total LDL (L5%) and L5 concentration increased with the number of MetS criteria (P<0.001). L5% correlated with classic CVD risk factors, including waist circumference, body mass index, waist-to-height ratio, smoking status, blood pressure, and levels of fasting plasma glucose, triglyceride, and high-density lipoprotein. Stepwise regression analysis revealed that fasting plasma glucose level and body mass index contributed to 28% of L5% variance. The L5 concentration was associated with CVD risk and contributed to 11% of 30-year general CVD risk variance when controlling the variance of waist circumference.

CONCLUSION

Our findings show that LDL electronegativity was associated with multiple CVD risk factors and CVD risk, suggesting that the LDL electronegativity index may have the potential to be a novel index for predicting CVD. Large-scale clinical trials are warranted to test the reliability of this hypothesis and the clinical importance of the LDL electronegativity index.

Effects of fibroblast growth factor 21 on cell damage in vitro and atherosclerosis in vivo

Fibroblast growth factor 21 (FGF-21), which is a modulator of glucose and lipid homeostasis, acts as a novel therapeutic reagent for many metabolic perturbations. However, its potential as a treatment for cardiovascular disease, especially atherosclerosis (AS) has not been fully explored. Here, we report that recombinant FGF-21 improves resistance to cell damage from oxidative stress in vitro, and from atherosclerosis in vivo. Human umbilical vein endothelial cells (HUVECs) were induced with H2O2, followed by treatment with high purity recombinant FGF-21. The results indicated that FGF-21 significantly enhanced cell viability and decreased the degree of DNA fragmentation in HUVECs, as caused by H2O2 stress induction. Further studies revealed that FGF-21 inhibited H2O2-induced cell apoptosis by preventing the activation of mitogen-activated protein kinase (MAPK) signaling pathways. In an established rat model, FGF-21 dramatically improved the condition of atherosclerotic rats by decreasing serum levels of total triglyceride (TG), low density lipoprotein cholesterol (LDL-C), and total cholesterol (TC), and by increasing the serum levels of high density lipoprotein cholesterol (HDL-C). FGF-21 also has antioxidant effects in the atherosclerotic rat, such that increased levels of superoxide dismutase, reduced glutathione, and reduced malondialdehyde were observed. These data provide novel insight into the potential use of FGF-21 in the prevention and treatment of human cardiovascular diseases.

Dehydroglyasperin C, a component of liquorice, attenuates proliferation and migration induced by platelet-derived growth factor in human arterial smooth muscle cells

Liquorice is one of the botanicals used frequently as a traditional medicine in the West and in the East. Platelet-derived growth factor (PDGF)-BB is involved in the development of CVD by inducing abnormal proliferation and migration of vascular smooth muscle cells. In our preliminary study, dehydroglyasperin C (DGC), an active compound of liquorice, showed strong antioxidant activity. Since phytochemicals with antioxidant activities showed beneficial effects on chronic inflammatory diseases, the present study aimed to investigate the effects of DGC on PDGF-induced proliferation and migration of human aortic smooth muscle cells (HASMC). Treatment of HASMC with DGC for 24 h significantly decreased PDGF-induced cell number and DNA synthesis in a dose-dependent manner without any cytotoxicity, as demonstrated by the 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide test and thymidine incorporation. Upon cell cycle analysis, DGC blocked the PDGF-induced progression through the G0/G1 to S phase of the cell cycle, and down-regulated the expression of cyclin-dependent kinase (CDK); 2, cyclin E, CDK4 and cyclin D1. Furthermore, DGC significantly attenuated PDGF-stimulated phosphorylation of PDGF receptor-b, phospholipase C-g1, AKT and extracellular-regulated kinase 1/2, and DGC inhibited cell migration and the dissociation of actin filaments by PDGF. In a rat vascular balloon injury model, DGC suppressed an excessive reduction in luminal diameters and neointimal formation compared with the control group. These results demonstrate the mechanistic basis for the prevention of CVD and the potential therapeutic properties of DGC.

Relationship between oxidative stress and apoptotic markers in lymphocytes of diabetic patients with chronic non healing wound

AIMS

Hyperglycemia causes generation of free radicals which leads to oxidative stress and apoptosis in various cells. The present study was undertaken to investigate the correlation between oxidative stress and apoptotic markers in lymphocytes of diabetic patients with chronic non healing wounds.

METHODS

Thirty healthy, thirty uncontrolled type 2 diabetes mellitus (T2DM) and thirty uncontrolled T2DM with chronic, non healing, neuropathic diabetic foot patients were included in this study. Indices of oxidative stress inside the lymphocyte lysate were estimated by measuring content of superoxide dismutase (SOD), Catalase, Glutathione and malonaldialdehyde (MDA). Protein expression studies of pro and anti apoptotic markers were carried out to elucidate their possible involvement in diabetic context.

RESULTS

SOD and MDA activity was significantly higher in the lymphocytes of diabetic patients having chronic, non healing diabetic wound as compared with healthy (p<0.001); whereas catalase and GSH activity was significantly reduced (p<0.001) in the same group. Expressions of pro apoptotic markers (Caspase-3, Fas and Bax) were significantly higher whereas reduced expression of anti-apoptotic marker (Bcl-2) were obtained in lymphocytes of diabetic and non diabetic individuals.

CONCLUSIONS

Hyperglycemia confers pro apoptotic manifestations which are mostly through altered indices of oxidative stress within lymphocytic milieu.

Effects of clopidogrel on vascular proliferation and apoptosis in an atherosclerotic rabbit model

Inflammation, vascular proliferation. and apoptosis contribute to the process of atherosclerosis. Clopidogrel has been used to treat atherosclerosis; however, the mechanism is not entirely known. Compared with those of atorvastatin, we determined effects of clopidogrel on inflammatory factors, vascular proliferation, and apoptosis in an atherosclerosis rabbit model. New Zealand white rabbits were fed a normal diet or a high cholesterol diet for 7 weeks. The right iliac artery of animals except those in the negative control group were balloon-injured 1 week after initiation of the diet, and groups of animals were treated with clopidogrel (4 mg/kg per day), atorvastatin (2.5 mg/kg per day), or placebo (positive control group) for 6 weeks. We found that the placebo group had significant progression of atherosclerosis compared with the negative control group. In contrast, clopidogrel- or atorvastatin-treated rabbits showed a significant reduction in progression of atherosclerosis, including a low expression of high sensitivity C-reactive protein and platelet-derived growth factor, a reduced intima thickness, and reduced ratio of bcl-2/bax in the vascular wall. These results suggest that clopidogrel can retard the progression of established lesions that is related to inhibiting inflammation, cell proliferation, and promotion of cell apoptosis.

Mechanisms of inhibiting proliferation of vascular smooth muscle cells by serum of rats treated with Dahuang Zhechong pill

Dahuang Zhechong pill (DHZCP), a famous and classical Chinese herbal prescription, consists of twelve traditional Chinese drugs: Eupolyphaga sinensis Walker., Rheum officinale Baill., Scutellaria baicalensis Georgi., Glycyrrhiza uralensis Fisch., Prunus persica Batsch., Prunus armeniaca L., Paeonia lactiflora Pall., Rehmannia glutinosa Libosch., Toxicodendron vernicifluum F.A. Barkl., Tabanus bivittatus Mats., Hirudo nipponica Whitman. and Holotrichia diomphalia Bates., and is clinically used to treat hepatic diseases, gynecopathy and atherosclerosis in China. Our previous studies confirm that DHZCP is able to significantly inhibit proliferation of vascular smooth muscle cells (VSMCs) in vivo and in vitro.

AIM OF THE STUDY

To investigate the mechanisms of inhibition of VSMCs proliferation by DHZCP with the method of Serum Pharmacology.

MATERIALS AND METHODS

VSMCs proliferation of rat was assayed by measuring the cell viability with the MTT method, and platelet-derived growth factor (PDGF) expression in VSMCs was examined by the immunocytochemical method. Cycle and apoptosis of VSMCs were evaluated with flow cytometry.

RESULTS

The serum of DHZCP-treated rats not only inhibited endothelin-1 (ET-1) stimulated cell proliferation and PDGF expression in VSMCs, but also promoted apoptosis of the proliferated VSMCs. Meanwhile, the serum of rats containing DHZCP interfered with the cycle of PDGF-stimulated VSMCs, increasing proportion of the cells in G(0)/G(1) phases and decreasing proportion of the cells in S and G(2)/M phases.

CONCLUSION

These suggest that the inhibitory effect of DHZCP on VSMCs proliferation is partially attributed to depressing PDGF expression in VSMCs, retarding the cell cycle and to promoting apoptosis of VSMCs.

Electronegative LDL impairs vascular endothelial cell integrity in diabetes by disrupting fibroblast growth factor 2 (FGF2) autoregulation

OBJECTIVE

L5, a circulating electronegative LDL identified in patients with hypercholesterolemia or type 2 diabetes, induces endothelial cell (EC) apoptosis by suppressing fibroblast growth factor (FGF)2 expression. FGF2 plays a pivotal role in endothelial regeneration and compensatory arteriogenesis. It is likely that vasculopathy and poor collateralization in diabetes is a result of FGF2 dysregulation.

RESEARCH DESIGN AND METHODS

To investigate this mechanism, we isolated L5 from type 2 diabetic patients. In cultured bovine aortic ECs (BAECs), L5 inhibited FGF2 transcription and induced apoptosis. Because FGF2 stimulates the phosphatidylinositol 3-kinase (PI3K)-Akt pathway, we examined whether FGF2 transcription is regulated by Akt through a feedback mechanism.

RESULTS

Diabetic L5 reduced FGF2 release to the medium but enhanced caspase-3 activity, with resultant apoptosis. Inhibition of PI3K with wortmannin or suppression of Akt activation with dominant-negative Akt inhibited FGF2 expression. Transfection of BAECs with FGF2 antisense cDNA depleted endogenous FGF2 protein. In these cells, not only was Akt phosphorylation inhibited, but FGF2 transcription was also critically impaired. In contrast, transfecting BAECs with FGF2 sense cDNA augmented Akt phosphorylation. Treatment with constitutively active Akt enhanced FGF2 expression. Augmentation of either FGF2 transcription or Akt phosphorylation rendered BAECs resistant to L5.

CONCLUSIONS

These findings suggest that FGF2 is the primary initiator of its own expression, which is autoregulated through a novel FGF2-PI3K-Akt loop. Thus, by disrupting FGF2 autoregulation in vascular ECs, L5 may impair reendothelialization and collateralization in diabetes.

Lymphocyte resistance to lysophosphatidylcholine mediated apoptosis in atherosclerosis

OBJECTIVE

Apoptosis is being increasingly regarded as a key component in the development and progression of atherosclerosis. Since it has become apparent that the immune system plays a predominant role in mediating atherogenesis, there has been a growing recognition that the evaluation of lymphocyte apoptosis may contribute to understanding a persistent altered immune and inflammatory response. The aim of the present study was to evaluate the apoptotic effect of lysophosphatidylcholine (LPC) on peripheral blood lymphocytes (PBL) derived from unstable angina (UA) patients, as compared to healthy donors.

METHODS

PBL isolated from 27 healthy donors and 25 age matched UA patients were examined. Early apoptotic events induced by LPC in resting and phytohemagglutinin (PHA)-activated lymphocytes were evaluated by several apoptotic assays. The levels of intracellular reactive oxygen species (ROS) and the expression of apoptotic regulated proteins (Bcl-2 and Bax) were measured.

RESULTS

LPC was found to induce apoptosis in normal activated lymphocytes, in a dose- and time-dependent manner, in association with an increase in intracellular ROS. In UA patients, an exposure of PHA-activated PBL to LPC triggered neither an increase in ROS generation, nor in the apoptotic manifestations, and was associated with a significantly lower ratio of Bax/Bcl-2 expression.

CONCLUSION

Our results indicate that PBL isolated from UA patients may be resistant to apoptosis induction by LPC, resulting from oxidative stress challenge and dysregulation of apoptosis-related protein expression.

Markers for silent myocardial ischemia in diabetes. Are they helpful?

Silent myocardial ischemia (SMI) and silent coronary stenoses (CS) are two to seven times more frequent in diabetic patients than in non-diabetic patients. In addition to this, they have a higher predictive value for cardiovascular events than the classical cardiovascular risk factors, either taken alone or combined. Coronary arterial disease is the leading cause of mortality and morbidity in the diabetic population. Altogether, these data suggest that screening for SMI and silent CS is an important issue. We assume that detecting SMI and silent CS improves patient management, and leads to optimised follow-up, action taken on nutrition, exercise and lifestyle, management of the cardiovascular risk factors, and revascularisation procedures whenever possible. However, screening for SMI and silent CS is expensive and may induce morbidity. Selecting the patients with a high a priori risk of SMI and silent CS is therefore of major concern. Carotid or lower limb peripheral arterial disease, proteinuria, male gender, an age greater than 60 years, and two or more cardiovascular risk factors among smoking, microalbuminuria, dyslipidemia, hypertension, a family history of premature cardiac disease, and cardiac autonomic neuropathy have been demonstrated to be the best current predictors of SMI and silent CS. New markers, such as adhesion molecules, Lp(a), inflammation parameters or homocysteine, and endothelium function assessment might be of further help in the future.

Fas/Fas-Ligand pathway is impaired in patients with type 2 diabetes. Influence of hypertension and insulin resistance

OBJECTIVES

In type 2 diabetic patients with no cardiac history or symptoms, 1) to evaluate whether the soluble forms of Fas (sFas) and Fas-ligand (sFasL), involved in apoptosis, may be markers of silent coronary disease or related to hypertension or microangiopathic complications; 2) to examine the effect of short-term glycemic control on sFas and sFasL.

METHODS

(1) sFas and sFasL were measured with the ELISA method in 44 asymptomatic diabetic patients, 33 with hypertension, and with a normal myocardial scintigraphy (n=14), with silent myocardial ischemia (SMI) and without (n=15) or with (n=15) significant coronary stenoses; and in 14 controls; (2) sFas and sFasL were measured in 15 poorly controlled diabetic patients before and after 7 days of CSII treatment.

RESULTS

(1) sFas and sFasL differed in the four groups of patients (p=0.003 each). sFas was significantly higher in the patients with SMI without (p=0.035) and with coronary stenoses (p=0.002) than in the control group. sFasL was lower in the three groups of diabetic patients (p<0.05 each) than in control group. In the diabetic population, sFas correlated positively with hypertension (p=0.021), and sFasL negatively with hypertension (p=0.027) and HOMA index in the non-insulin treated patients (p=0.049); (2) sFas did not differ before or after CSII, and there was a marginal decrease in sFasL.

CONCLUSION

Fas-mediated apoptosis is involved in type 2 diabetes and might be associated with hypertension and/or its vascular consequences. sFasL might be affected by insulin resistance. sFas and sFasL are not effective markers of SMI.

The role of notch in modeling and maintaining the vasculature

The Notch proteins encompass a family of transmembrane receptors that have been highly conserved through evolution as mediators of cell fate, and are comprised of 4 members in mammals (Notch1 to Notch4). Following intra cellular processing of the full-length protein, Notch is expressed at the cell surface as a heterodimeric receptor. Engagement by ligand results in a 2-step cleavage of the Notch heterodimer, releasing the intracellular domain of Notch and allowing translocation to the nucleus. The intracellular domain of Notch interacts with the DNA-binding factor, CSL, resulting in transactivation at various promoters, in particular those of various basic helix-loop-helix factors of the HES (Hairy and Enhancer of Split) and HRT families (Hairy-Related Transcription factor). Recent findings implicate Notch as playing a critical and non-redundant role in vascular development and maintenance. This article briefly reviews vessel development and Notch signaling and highlights studies that examine Notch functions such as proliferation, cell survival, migration, adhesion, and mesenchymal transformation in the vasculature. Human diseases caused by Notch pathway members are also discussed.Key words: vascular, endothelial, Notch, angiogenesis, mesenchymal transformation.

Inhibiting effect of selenium on oxysterols-induced apoptosis of rat vascular smooth muscle cells

To evaluate the cytoprotection mechanism of selenium against cholestane-3beta,5alpha,6beta-triol (3-triol)-induced vascular smooth muscle cells (VSMCs) damage, cell viability was analyzed by 3-(4,5-dimethylthiazol-2 -yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cell count, the percentage release of lactate dehydrogenase (LDH) from the cell was assessed, and apoptosis was detected by DNA laddering and flow cytometric analysis. Meanwhile, the activity of glutathione peroxidase (GPx) of VSMCs was measured. The results showed that 3-triol could inhibit proliferation of VSMCs time-dependently and dose-dependently, increase the percentage release of LDH and induce VSMCs apoptosis. While the cytotoxicity and cells apoptosis induced by 3-triol was attenuated by pretreatment of cells with low concentration of sodium selenite, and the longer the pretreated time was, the stronger the inhibition was. Preincubation of cells with sodium selenite (50 nM) for 12 or 24 h before 1, 5, 10, 25, or 50 microM 3-triol exposure, the cell viabilities increased 28.5% (P<0.05), 18.3%, 197.6% (P<0.01), 66.7%, 50.0% or 35.1% (P<0.05), 62.3% (P<0.05), 329.6% (P<0.01), 221.3% (P<0.05), 74.0% compared with the control cells, respectively. When the cells were preincubated with sodium selenite (50 nM) for 12 or 24 h before exposure to 3-triol (10 microM), the percent of apoptotic cells reduced from 30.47+/-15.34% to 26.88+/-17.32% or 7.41+/-5.46% (P<0.05). With preincubation of sodium selenite (50 nM) for 24 h, the GPx activity of VSMCs increased 18.5% compared with control (P<0.05). In conclusion, the results suggested that incubated VSMCs could absorb and transfer selenite as selenoprotrein, such as GPx, if the time is long enough and VSMCs selenoproteins can protect markedly against apoptosis and damage induced by 3-triol in VSMCs.

Synthesis of immune modulators by smooth muscles

The primary function of smooth muscle cells is to contract and alter the stiffness or diameter of hollow organs such as blood vessels, the airways and the gastrointestinal and urogenital tracts. In addition to purely structural functions, smooth muscle cells may play important metabolic roles, particularly in various inflammatory responses. In cell culture, these cells have been shown to be metabolically dynamic, synthesizing and secreting extracellular matrix proteins, glycosaminoglycans and a wide variety of cell-cell signaling proteins, such as interleukins, chemokines and peptide growth factors. Secreted cell signaling proteins participate in the inflammatory response of smooth muscle-containing organs, and some can also stimulate smooth muscle migration, proliferation and contraction. The cellular signaling pathways controlling synthesis of these signaling proteins are similar to those used by cells mediating innate immunity and may contribute to pathogenesis of diverse diseases including atherosclerosis, asthma, inflammatory bowel diseases and preterm labor. Appreciating the role of smooth muscle cells in these diseases may lead to better understanding of the beneficial effects of anti-inflammatory drugs as well as identification of new targets for anti-inflammatory therapy.

Notch4 inhibits endothelial apoptosis via RBP-Jkappa-dependent and -independent pathways

Notch4, a member of the Notch family of transmembrane receptors, is expressed primarily on endothelial cells. Activation of Notch in various cell systems has been shown to regulate cell fate decisions, partly by regulating the propensity of cells to live or die. Various studies have demonstrated a role for Notch1 in modulating apoptosis, either in a positive or negative manner. In this study, we determined that constitutively active Notch4 (Notch4 intracellular domain) inhibited endothelial apoptosis triggered by lipopolysaccharide. Notch signals are transmitted by derepression and coactivation of the transcriptional repressor, RBP-Jkappa, as well as by less well defined mechanisms that are independent of RBP-Jkappa. A Notch mutant lacking the N-terminal RAM domain showed only partial antiapoptotic activity relative to Notch4 intracellular domain but stimulated equivalent RBP-Jkappa-dependent transcriptional activity. Similarly, constitutively active RBP-Jkappa activated a full transcriptional response but only demonstrated partial antiapoptotic activity. Additional studies suggest that Notch4 provides endothelial protection in two ways: inhibition of the JNK-dependent proapoptotic pathway in an RBP-Jkappa-dependent manner and induction of an antiapoptotic pathway through an RBP-Jkappa-independent up-regulation of Bcl-2. Our findings demonstrate that Notch4 activation inhibits apoptosis through multiple pathways and provides one mechanism to explain the remarkable capacity of endothelial cells to withstand apoptosis.

Survivin study: what is the next wave?

Survivin, a novel member of inhibitor of apoptosis (IAP) protein family, is aberrantly expressed in cancer but undetectable in normal, differentiated adult tissues. Current studies suggest that survivin is implicated in both control of apoptosis and regulation of cell division. However, due to some inconsistent observations on survivin subcellular localization, there is debate about survivin's function in regulating apoptosis, cell division, or both. This review will discuss concepts, experimental methods, and interesting results that unify the different notions about survivin localization and function or point out gaps of knowledge about controversial issues. The author also intends to review various aspects of survivin studies, which were not emphasized or sufficiently discussed in previous reviews on survivin, and update recent developments that may reveal new applications of disease-oriented therapeutics in the coming years.

Verapamil reduces coronary endothelium damage and cardiomyocyte necrosis but not apoptosis after ischemia and reperfusion: ex-vivo study in rat hearts

We tested the hypothesis of beneficial effects of the calcium-blocker verapamil in a model of ischemia-reperfusion, and investigated its effects against coronary microcirculation and cardiomyocyte apoptosis. Isolated working rat hearts were subjected to 15 min global ischemia and 22-180 min reperfusion in the presence or absence of verapamil (0.25 &mgr;M). We evaluated creatinephosphokinase (CK) in coronary effluent, heart weight changes, microvascular permeability (extravasation of fluoresceine-labeled albumin), ultrastructural alterations, and cardiomyocyte apoptosis (by 1.5% agarose gel electrophoresis and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling technique). In this model, 0.25 &mgr;M verapamil significantly reduced myocardial damage, CK release and vascular hyperpermeability, concomitant with a reduction in endothelial and cardiomyocyte lesions; on the contrary, 0.25 &mgr;M verapamil was unable to reduce cardiomyocyte apoptosis. In conclusion, in the absence of perfusing granulocytes, the acute administration of a pharmacologically relevant verapamil concentration reduces ischemia-reperfusion injury and prevents coronary endothelial cell and cardiomyocyte necrotic cell death but it is unable to reduce apoptotic cell death in isolated working rat hearts.