Retinoids: versatile biological response modifiers of vascular smooth muscle phenotype

Selective mural cell recruitment of pericytes to networks of assembling endothelial cell-lined tubes

Mural cells are critically important for the development, maturation, and maintenance of the blood vasculature. Pericytes are predominantly observed in capillaries and venules, while vascular smooth muscle cells (VSMCs) are found in arterioles, arteries, and veins. In this study, we have investigated functional differences between human pericytes and human coronary artery smooth muscle cells (CASMCs) as a model VSMC type. We compared the ability of these two mural cells to invade three-dimensional (3D) collagen matrices, recruit to developing human endothelial cell (EC)-lined tubes in 3D matrices and induce vascular basement membrane matrix assembly around these tubes. Here, we show that pericytes selectively invade, recruit, and induce basement membrane deposition on EC tubes under defined conditions, while CASMCs fail to respond equivalently. Pericytes dramatically invade 3D collagen matrices in response to the EC-derived factors, platelet-derived growth factor (PDGF)-BB, PDGF-DD, and endothelin-1, while minimal invasion occurs with CASMCs. Furthermore, pericytes recruit to EC tube networks, and induce basement membrane deposition around assembling EC tubes (narrow and elongated tubes) when these cells are co-cultured. In contrast, CASMCs are markedly less able to perform these functions showing minimal recruitment, little to no basement membrane deposition, with wider and shorter tubes. Our new findings suggest that pericytes demonstrate much greater functional ability to invade 3D matrix environments, recruit to EC-lined tubes and induce vascular basement membrane matrix deposition in response to and in conjunction with ECs.

Is it time for a retinoic acid-eluting stent or retinoic acid-coated balloon? Insights from experimental studies of systemic and local delivery of retinoids

Although the incidence of restenosis and stent thrombosis has substantially declined during the last decades, they still constitute the two major causes of stent failure. These complications are partially attributed to the currently used cytostatic drugs, which can cause local inflammation, delay or prevent re-endothelialization and essentially cause arterial cell toxicity. Retinoic acid (RA), a vitamin A (retinol) derivative, is a naturally occurring substance used for the treatment of cell proliferation disorders. The agent has pleiotropic effects on vascular smooth muscle cells and macrophages: it influences the proliferation, migration, and transition of smooth muscle cells to other cell types and modulates macrophage activation. These observations are supported by accumulated evidence from in vitro and in vivo experiments. In addition, systemic and topical administration of RA can decrease the development of atherosclerotic plaques and reduce or inhibit restenosis after vascular injury (caused by embolectomy, balloon catheters, or ligation of arteries) in various experimental models. Recently, an RA-drug eluting stent (DES) has been tested in an animal model. In this review, we explore the effects of RA in atherosclerosis and the potential of the local delivery of RA through an RA-DES or RA-coated balloon for targeted therapeutic percutaneous vascular interventions. Despite promising published results, further experimental study is warranted to examine the safety and efficacy of RA-eluting devices in vascular artery disease.

Huotan Jiedu Tongluo Decoction Inhibits Balloon-Injury-Induced Carotid Artery Intimal Hyperplasia in the Rat through the PERK-eIF2α-ATF4 Pathway and Autophagy Mediation

In-stent restenosis (ISR) is the main factor affecting the outcome of percutaneous coronary intervention (PCI), and its main pathological feature is neointimal hyperplasia. Huotan Jiedu Tongluo decoction (HTJDTLD) is an effective traditional Chinese medicine (TCM) prescription for the treatment of vascular stenosis diseases. However, the precise anti-ISR mechanism of HTJDTLD remains unclear. Here, we investigated whether HTJDTLD can inhibit the excessive activation of endoplasmic reticulum stress (ERS) and reduce the level of autophagy factors through regulating the PERK-eIF2α-ATF4 pathway, thereby inhibiting the proliferation of the intima of blood vessels damaged by balloon injury (BI) and preventing the occurrence of ISR. In this study, a 2F Fogarty balloon was used to establish a common carotid artery (CCA) BI model in male Sprague-Dawley rats. Then, HTJDTLD (16.33 g/kg/d) or atorvastatin (1.19 mg/kg/d) was administered by gavage. Four weeks later, hematoxylin-eosin (HE) and Masson staining of the injured CCA were performed to observe the histological changes in the CCA. Immunohistochemistry (IHC) was used to assess the proliferation and dedifferentiation of vascular smooth muscle cells (VSMCs) in the CCA. Western blotting and RT-PCR were used to measure the expression of ERS- and autophagy-related proteins and mRNAs in the CCA. The results indicated that HTJDTLD significantly alleviated BI-induced carotid artery intimal hyperplasia and fibrosis and reduced the neointimal area (NIA) and NIA/medial area (MA) ratio. In addition, HTJDTLD inhibited the proliferation and dedifferentiation of VSMCs, reduced the expression of proliferating cell nuclear antigen (PCNA), and increased the smooth-muscle-α-actin- (SMα-actin-) positive area. HTJDTLD also significantly reduced the expression of the ERS-related factors: GRP78, p-PERK/PERK, p-eIF2α/eIF2α, ATF4, and CHOP. In addition, the expression of the autophagy-related factors, Beclin1, LC3B, and ATG12, was significantly decreased. In addition, in vitro experiments showed that HTJDTLD inhibited the above-mentioned ERS signal molecules in human umbilical vein endothelial cells (HUVEC) and rat aortic smooth muscle cells (A7R5) induced by tunicamycin (TM) and played a crucial role in protecting cells from damage. HTJDTLD may be a very promising drug for the treatment of ISR.

Fate and State of Vascular Smooth Muscle Cells in Atherosclerosis

Vascular smooth muscle cells (VSMCs) have long been associated with phenotypic modulation/plasticity or dedifferentiation. Innovative technologies in cell lineage tracing, single-cell RNA sequencing, and human genomics have been integrated to gain unprecedented insights into the molecular reprogramming of VSMCs to other cell phenotypes in experimental and clinical atherosclerosis. The current thinking is that an apparently small subset of contractile VSMCs undergoes a fate switch to transitional, multipotential cells that can adopt plaque-destabilizing (inflammation, ossification) or plaque-stabilizing (collagen matrix deposition) cell states. Several candidate mediators of such VSMC fate and state changes are coming to light with intriguing implications for understanding coronary artery disease risk and the development of new treatment modalities. Here, we briefly summarize some technical and conceptual advancements derived from 2 publications in Circulation and another in Nature Medicine that, collectively, illuminate new research directions to further explore the role of VSMCs in atherosclerotic disease.

Early inhibition of endothelial retinoid uptake upon myocardial infarction restores cardiac function and prevents cell, tissue, and animal death

Physiologically, following myocardial infarction (MI), retinoid levels elevate locally in the infarcted area. Whereas therapeutic systemic application of retinoids was shown to reduce the progression of ventricular dilatation and the onset of heart failure, the role of acute physiologically increased retinoids in the infarction zone is unknown to date. To reveal the role of local retinoids in the MI zone is the central aim of this study. Using human cell culture and co-culture models for hypoxia as well as various assays systems, lentivirus-based transgene expression, in silico molecular docking studies, and an MI model in rats, we analysed the impact of the retinoid all-trans retinoic acid (ATRA) on cell signalling, cell viability, tissue survival, heart function, and MI-induced death in rats. Based on our results, ATRA-mediated signalling does aggravate the MI phenotype (e.g. 2.5-fold increased mortality compared to control), whereas 5'-methoxyleoligin (5ML), a new agent which interferes with ATRA-signalling rescues the ATRA-dependent phenotype. On the molecular level, ATRA signalling causes induction of TXNIP, a potent inhibitor of the physiological antioxidant thioredoxin (TRX1) and sensitizes cells to necrotic cell death upon hypoxia. 5ML-mediated prevention of ATRA effects were shown to be based on the inhibition of cellular ATRA uptake by interference with the cholesterol (and retinol) binding motif of the transmembrane protein STRA6. 5ML-mediated inhibition of ATRA uptake led to a strong reduction of ATRA-dependent gene expression, reduced ROS formation, and protection from necrotic cell death. As 5ML exerted a cardioprotective effect, also independent of its inhibition of cellular ATRA uptake, the agent likely has another cardioprotective property, which may rely on the induction of TRX1 activity. In summary, this is the first study to show i) that local retinoids in the early MI zone may worsen disease outcome, ii) that inhibition of endothelial retinoid uptake using 5ML may constitute a novel treatment strategy, and iii) that targeting endothelial and myocardial retinoid uptake (e.g. via STRA6 inhibition) may constitute a novel treatment target in acute MI.

Human Adipose-Derived and Amniotic Fluid-Derived Stem Cells: A Preliminary In Vitro Study Comparing Myogenic Differentiation Capability

Background

Around the world, disabilities due to musculoskeletal disorders have increased and are a major health problem worldwide. In recent years, stem cells have been considered to be powerful tools for musculoskeletal tissue engineering. Human adipose-derived stem cells (hADSCs) and amniotic fluid-derived stem cells (hAFSCs) undergo typical differentiation process into cells of mesodermal origin and can be used to treat muscular system diseases. The aim of the present study was to compare the biological characteristic of stem cells isolated from different human tissues (adipose tissue and amniotic fluid) with respect to myogenic capacity and skeletal and smooth muscle differentiation under the same conditions.

Material/Methods

hAFSCs and hADSCs were isolated during standard medical procedures and widely characterized by specific markers expression and differentiation potential. Both cell types were induced toward smooth and striated muscles differentiation, which was assessed with the use of molecular techniques.

Results

For phenotypic characterization, both stem cell types were assessed for the expression of OCT-4, SOX2, CD34, CD44, CD45, and CD90. Muscle-specific markers appeared in both stem cell types, but the proportion of positive cells showed differences depending on the experimental conditions used and the source from which the stem cells were isolated.

Conclusions

In this study, we demonstrated that hADSCs and hAFSCs have different capability of differentiation toward both muscle types. However, hADSCs seem to be a better source for myogenic protocols and can promote skeletal and smooth muscle regeneration through either direct muscle differentiation or by paracrine mechanism.

Massive Effect on LncRNAs in Human Monocytes During Fungal and Bacterial Infections and in Response to Vitamins A and D

Mycoses induced by C.albicans or A.fumigatus can cause important host damage either by deficient or exaggerated immune response. Regulation of chemokine and cytokine signaling plays a crucial role for an adequate inflammation, which can be modulated by vitamins A and D. Non-coding RNAs (ncRNAs) as transcription factors or cis-acting antisense RNAs are known to be involved in gene regulation. However, the processes during fungal infections and treatment with vitamins in terms of therapeutic impact are unknown. We show that in monocytes both vitamins regulate ncRNAs involved in amino acid metabolism and immune system processes using comprehensive RNA-Seq analyses. Compared to protein-coding genes, fungi and bacteria induced an expression change in relatively few ncRNAs, but with massive fold changes of up to 4000. We defined the landscape of long-ncRNAs (lncRNAs) in response to pathogens and observed variation in the isoforms composition for several lncRNA following infection and vitamin treatment. Most of the involved antisense RNAs are regulated and positively correlated with their sense protein-coding genes. We investigated lncRNAs with stimulus specific immunomodulatory activity as potential marker genes: LINC00595, SBF2-AS1 (A.fumigatus) and RP11-588G21.2, RP11-394l13.1 (C.albicans) might be detectable in the early phase of infection and serve as therapeutic targets in the future.

Tamibarotene Ameliorates Bleomycin-Induced Dermal Fibrosis by Modulating Phenotypes of Fibroblasts, Endothelial Cells, and Immune Cells

Tamibarotene (Am80) is a synthetic retinoid that modulates the pathologic processes of various autoimmune and inflammatory diseases and their animal models. We here investigated the therapeutic potential of Am80 against systemic sclerosis using its animal models. Am80 significantly attenuated dermal and hypodermal fibrosis in bleomycin (BLM)-treated mice and tight skin 1 mice, respectively. Consistently, Am80 significantly suppressed the expression of various molecules related to tissue fibrosis, including transforming growth factor-β1, connective tissue growth factor, IL-4, IL-10, IL-13, IL-17A, tumor necrosis factor-α, IFN-γ, and monocyte chemotactic protein 1 in the lesional skin of BLM-treated mice. Furthermore, Am80 decreased the proportion of effector T cells, while increasing that of naïve T cells among CD4+ T cells in the draining lymph nodes of BLM-treated mice. Moreover, a series of BLM-induced pathologic events, including endothelial-to-mesenchymal transition; ICAM-1 expression in endothelial cells; the infiltration of macrophages, mast cells, and lymphocytes; and M2 macrophage differentiation, were attenuated by Am80. Importantly, Am80 directly reversed the profibrotic phenotype of transforming growth factor-β1-treated dermal fibroblasts, suppressed ICAM-1 expression in endothelial cells, and promoted M1 macrophage differentiation in vitro. Collectively, Am80 inhibits the development of experimental dermal fibrosis by reversing the profibrotic phenotype of various cell types and would be a candidate for therapeutic drugs against dermal fibrosis of systemic sclerosis.

All-trans-retinoic Acid Increases SLC26A3 DRA (Down-regulated in Adenoma) Expression in Intestinal Epithelial Cells via HNF-1β

All-trans-retinoic acid (ATRA) is an active vitamin A derivative known to modulate a number of physiological processes, including growth and development, differentiation, and gene transcription. The protective effect of ATRA in gut inflammation and diarrheal diseases has been documented. In this regard, down-regulated in adenoma (DRA, a key luminal membrane Cl(-) transporter involved in NaCl absorption) has been shown to be suppressed in intestinal inflammation. This suppression of DRA is associated with diarrheal phenotype. Therefore, current studies were undertaken to examine the effects of ATRA on DRA expression. DRA mRNA levels were significantly elevated (∼4-fold) in response to ATRA with induction starting as early as 8 h of incubation. Similarly, ATRA increased DRA protein expression by ∼50%. Furthermore, DRA promoter activity was significantly increased in response to ATRA indicating transcriptional activation. ATRA effects on DRA expression appeared to be mediated via the RAR-β receptor subtype, as ATRA remarkably induced RAR-β mRNA levels, whereas RAR-β knockdown substantially attenuated the ability of ATRA to increase DRA expression. Results obtained from agonist (CH-55) and antagonist (LE-135) studies further confirmed that ATRA exerts its effects through RAR-β. Furthermore, ATRA treatment resulted in a significant increase in HNF-1β mRNA levels. The ability of ATRA to induce DRA expression was inhibited in the presence of HNF-1β siRNA indicative of its involvement in ATRA-induced effects on DRA expression. In conclusion, ATRA may act as an antidiarrheal agent by increasing DRA expression via the RAR-β/HNF-1β-dependent pathway.

Myocardin in biology and disease

Myocardin (MYOCD) is a potent transcriptional coactivator that functions primarily in cardiac muscle and smooth muscle through direct contacts with serum response factor (SRF) over cis elements known as CArG boxes found near a number of genes encoding for contractile, ion channel, cytoskeletal, and calcium handling proteins. Since its discovery more than 10 years ago, new insights have been obtained regarding the diverse isoforms of MYOCD expressed in cells as well as the regulation of MYOCD expression and activity through transcriptional, post-transcriptional, and post-translational processes. Curiously, there are a number of functions associated with MYOCD that appear to be independent of contractile gene expression and the CArG-SRF nucleoprotein complex. Further, perturbations in MYOCD gene expression are associated with an increasing number of diseases including heart failure, cancer, acute vessel disease, and diabetes. This review summarizes the various biological and pathological processes associated with MYOCD and offers perspectives to several challenges and future directions for further study of this formidable transcriptional coactivator.

Expression of cellular retinoic acid-binding protein-I (CRABP-I) in the cerebrospinal fluid of adult onset moyamoya disease and its association with clinical presentation and postoperative haemodynamic change

OBJECTIVE

The elevation of cellular retinoic acid-binding protein-I (CRABP-I) has been suggested as a candidate in the pathogenesis of paediatric moyamoya disease (MMD). However, few studies have addressed CRABP-I in adult onset MMD. The aim of this study was to examine the expression of CRABP-I in the cerebrospinal fluid (CSF) of adult onset MMD, and to evaluate its association with clinical presentation and postoperative haemodynamic change.

METHODS

This study examined the CSF from 103 patients: bilateral MMD, n=58 (56.3%); unilateral MMD, n=19 (18.4%); atherosclerotic cerebrovascular disease (ACVD), n=21 (20.4%); and control group, n=5 (4.9%). The intensity of CRABP-I was confirmed by western blotting and expressed as the median (25th-75th percentile). The differences in CRABP-I expression according to disease entity (unilateral MMD vs bilateral MMD vs ACVD), initial presenting symptoms (haemorrhage vs ischaemia) and postoperative haemodynamic change (vascular reserve in single photon emission CT and basal collateral vessels in digital subtraction angiography) were analysed.

RESULTS

CRABP-I intensities in bilateral MMD (1.45(0.86-2.52)) were significantly higher than in unilateral MMD (0.91(0.78-1.20)) (p=0.044) or ACVD (0.85(0.66-1.11)) (p=0.004). No significant differences were noted based on the initial presenting symptoms (p=0.687). CRABP-I was not associated with improvement in vascular reserve (p=0.327), but with decrease in basal collateral vessels (p=0.023) postoperatively.

CONCLUSIONS

Higher CRABP-I in the CSF can be associated with typical bilateral MMD pathogenesis in adults. Additionally, postoperative basal collateral change may be related to the degree of CRABP-I expression.

Effective Alu repeat based RT-Qpcr normalization in cancer cell perturbation experiments

Background

Measuring messenger RNA (mRNA) levels using the reverse transcription quantitative polymerase chain reaction (RT-qPCR) is common practice in many laboratories. A specific set of mRNAs as internal control reference genes is considered as the preferred strategy to normalize RT-qPCR data. Proper selection of reference genes is a critical issue, especially in cancer cells that are subjected to different in vitro manipulations. These manipulations may result in dramatic alterations in gene expression levels, even of assumed reference genes. In this study, we evaluated the expression levels of 11 commonly used reference genes as internal controls for normalization of 19 experiments that include neuroblastoma, T-ALL, melanoma, breast cancer, non small cell lung cancer (NSCL), acute myeloid leukemia (AML), prostate cancer, colorectal cancer, and cervical cancer cell lines subjected to various perturbations.

Results

The geNorm algorithm in the software package qbase+ was used to rank the candidate reference genes according to their expression stability. We observed that the stability of most of the candidate reference genes varies greatly in perturbation experiments. Expressed Alu repeats show relatively stable expression regardless of experimental condition. These Alu repeats are ranked among the best reference assays in all perturbation experiments and display acceptable average expression stability values (M<0.5).

Conclusions

We propose the use of Alu repeats as a reference assay when performing cancer cell perturbation experiments.

Expression and promoter analysis of a highly restricted integrin alpha gene in vascular smooth muscle

Full genome annotation requires gene expression analysis and elucidation of promoter activity. Here, we analyzed the expression and promoter of a highly restricted integrin gene, Itga8. RNase protection and quantitative RT-PCR showed Itga8 to be expressed most abundantly in vascular smooth muscle cells (SMC). Transcription start site mapping of Itga8 revealed the immediate 5' promoter region to be poorly conserved with orthologous sequences in the human genome. Further comparative sequence analysis showed a number of conserved non-coding sequence modules around the Itga8 gene. The immediate promoter region and an upstream conserved sequence module were each found to contain a CArG box, which is a binding site for serum response factor (SRF). Luciferase reporter assays revealed activity of several Itga8 promoter constructs with no apparent restricted activity to SMC types. Further, neither SRF nor its coactivator, Myocardin (MYOCD), was able to induce several distinct Itga8 promoter constructs. Transgenic mouse studies failed to reveal Itga8 promoter activity, indicating distal regulatory elements likely control this gene's in vivo expression profile. Interestingly, although the promoter was unresponsive to SRF/MYOCD, the endogenous Itga8 gene showed increases in expression upon ectopic MYOCD expression even though knockdown of SRF both in vitro and in vivo failed to demonstrate a corresponding change in Itga8. Collectively, these data demonstrate that Itga8 expression is CArG-SRF independent, but MYOCD dependent through an as yet unknown sequence module that is distal from the promoter region.

Using gene-network landscape to dissect genotype effects of TCF7L2 genetic variant on diabetes and cardiovascular risk

The single nucleotide polymorphism (SNP) within the TCF7L2 gene, rs7903146, is, to date, the most significant genetic marker associated with Type 2 diabetes mellitus (T2DM) risk. Nonetheless, its functional role in disease pathology is poorly understood. The aim of the present study was to investigate, in vascular smooth muscle cells from 92 patients undergoing aortocoronary bypass surgery, the contribution of this SNP in T2DM using expression levels and expression correlation comparison approaches, which were visually represented as gene interaction networks. Initially, the expression levels of 41 genes (seven TCF7L2 splice forms and 40 other T2DM relevant genes) were compared between rs7903146 wild-type (CC) and T2DM-risk (CT + TT) genotype groups. Next, we compared the expression correlation patterns of these 41 genes between groups to observe if the relationships between genes were different. Five TCF7L2 splice forms and nine genes showed significant expression differences between groups. RXRα gene was pinpointed as showing the most different expression correlation pattern with other genes. Therefore, T2DM risk alleles appear to be influencing TCF7L2 splice form's expression in vascular smooth muscle cells, and RXRα gene is pointed out as a treatment target candidate for risk reduction in individuals with high risk of developing T2DM, especially individuals harboring TCF7L2 risk genotypes.

RA-RAR-β counteracts myelin-dependent inhibition of neurite outgrowth via Lingo-1 repression

Central nervous system injury results in the release of molecules that inhibit neuronal regeneration, but retinoic acid counteracts this effect by inhibiting Lingo-1.

After an acute central nervous system injury, axonal regeneration is limited as the result of a lack of neuronal intrinsic competence and the presence of extrinsic inhibitory signals. The injury fragments the myelin neuronal insulating layer, releasing extrinsic inhibitory molecules to signal through the neuronal membrane–bound Nogo receptor (NgR) complex. In this paper, we show that a neuronal transcriptional pathway can interfere with extrinsic inhibitory myelin-dependent signaling, thereby promoting neurite outgrowth. Specifically, retinoic acid (RA), acting through the RA receptor β (RAR-β), inhibited myelin-activated NgR signaling through the transcriptional repression of the NgR complex member Lingo-1. We show that suppression of Lingo-1 was required for RA–RAR-β to counteract extrinsic inhibition of neurite outgrowth. Furthermore, we confirm in vivo that RA treatment after a dorsal column overhemisection injury inhibited Lingo-1 expression, specifically through RAR-β. Our findings identify a novel link between RA–RAR-β–dependent proaxonal outgrowth and inhibitory NgR complex–dependent signaling, potentially allowing for the development of molecular strategies to enhance axonal regeneration after a central nervous system injury.

Retinoid-induced expression and activity of an immediate early tumor suppressor gene in vascular smooth muscle cells

Retinoids are used clinically to treat a number of hyper-proliferative disorders and have been shown in experimental animals to attenuate vascular occlusive diseases, presumably through nuclear receptors bound to retinoic acid response elements (RARE) located in target genes. Here, we show that natural or synthetic retinoids rapidly induce mRNA and protein expression of a specific isoform of A-Kinase Anchoring Protein 12 (AKAP12β) in cultured smooth muscle cells (SMC) as well as the intact vessel wall. Expression kinetics and actinomycin D studies indicate Akap12β is a retinoid-induced, immediate-early gene. Akap12β promoter analyses reveal a conserved RARE mildly induced with atRA in a region that exhibits hyper-acetylation. Immunofluorescence microscopy and protein kinase A (PKA) regulatory subunit overlay assays in SMC suggest a physical association between AKAP12β and PKA following retinoid treatment. Consistent with its designation as a tumor suppressor, inducible expression of AKAP12β attenuates SMC growth in vitro. Further, immunohistochemistry studies establish marked decreases in AKAP12 expression in experimentally-injured vessels of mice as well as atheromatous lesions in humans. Collectively, these results demonstrate a novel role for retinoids in the induction of an AKAP tumor suppressor that blocks vascular SMC growth thus providing new molecular insight into how retiniods may exert their anti-proliferative effects in the injured vessel wall.

All-trans retinoic acid and a novel synthetic retinoid tamibarotene (Am80) differentially regulate CD38 expression in human leukemia HL-60 cells: possible involvement of protein kinase C-delta

ATRA and a synthetic RAR agonist tamibarotene (Am80) induce granulocytic differentiation of human acute leukemia HL-60 cells and have been used in antineoplastic therapy. ATRA induces CD38 antigen during HL-60 cell differentiation, which interacts with CD31 antigen on the vascular EC surface and may induce disadvantages in the therapy. We here examined the mechanisms of the ATRA-mediated CD38 induction and compared the difference between ATRA- and tamibarotene-mediated induction. Tamibarotene-induced HL-60 cell adhesion to ECs was 38% lower than ATRA, and NB4 cell adhesion to ECs by tamibarotene was equivalent to ATRA, which induced CD38 gene transcription biphasically in HL-60 cells, the early-phase induction via DR-RARE containing intron 1, and the delayed-phase induction via RARE lacking the 5'-flanking region. In contrast to ATRA, tamibarotene induced only the early-phase induction, resulting in its lower CD38 induction than ATRA. A PKCδ inhibitor, rottlerin, and siRNA-mediated PKCδ knockdown suppressed the ATRA-induced CD38 promoter activity of the 5'-flanking region, whereas a RAR antagonist, LE540, or RAR knockdown did not affect it. Cycloheximide and rottlerin suppressed the delayed-phase induction of CD38 expression by ATRA but did not affect the early-phase induction. Moreover, ATRA, but not tamibarotene, induced PKCδ expression without affecting its mRNA stability. The diminished effect of tamibarotene on CD38-mediated HL-60 cell adhesion to ECs compared with ATRA is likely a result of the lack of its delayed-phase induction of CD38 expression, which may be advantageous in antineoplastic therapy.

Polymorphisms in TGFB1 and PDGFRB are associated with Moyamoya disease in European patients

BACKGROUND

The etiology of Moyamoya disease (MMD) is still widely unknown. Several publications on Moyamoya describe differences of cytokine and growth factor concentrations in different specimen. We analyzed the DNA of patients with MMD for single nucleotide polymorphisms (SNPs) in and upstream of the genes for previously described associated cytokines and growth factors.

METHOD

Thirteen SNPs were genotyped in or upstream to four genes-basic fibroblast growth factor (BFGF), cellular retinoic acid-binding protein 1 (CRABP1), platelet derived growth factor receptor beta (PDGFRB), and transforming growth factor beta 1 (TGFB1)-comparing 40 DNA samples of MMD patients to 68 healthy controls from central Europe. Genotyping was performed by sequencing the SNP-containing genetic regions with custom made primers.

FINDINGS

We found association of two SNPs: rs382861 [A/C] (p = 0.0373, OR = 1.81, 95% CI = 1.03-3.17) in the promoter region of PDGFRB and rs1800471[C/G] (p = 0.0345, OR = 7.65, 95% CI = 0.97-59.95), located in the first exon of TGFB1.

CONCLUSION

Our results indicate possible genetic risk factors for the genesis of MMD. TGFB1 and PDGFRB are involved in vascular growth and transformation processes which may play a role in the development of MMD. Further analyses in larger European cohorts and replication in patients of different ethnicity, as well as functional studies, may lead to possible early detection of patients at risk for developing MMD and subsequently to future preventive therapies.

Retinol-binding protein-4 in experimental and clinical metabolic disease

Retinol-binding protein-4 (RBP4), a 21-kDa protein synthesized in the liver and adipose tissue, has recently been described as a murine adipokine involved in the development of insulin resistance. The expression of the gene encoding RBP4 was increased in the adipose tissue, but not in the liver, of insulin-resistant adipose GLUT4(-/-) mice and five other mouse models of obesity and insulin resistance. In addition, intraperitoneal injection or transgenic overexpression of RBP4 in mice induced insulin resistance. While experimental clinical approaches (mostly applying clamp techniques) in humans confirmed correlations of RBP4 with insulin resistance, studies in larger groups out of clinical routine failed to demonstrate a connection with alternative measures of insulin sensitivity. Yet, significant associations of RBP4 with atherogenic lipids were found and a focus of future studies should be the influence on atherosclerosis and related complications. Based on current data, the function of RBP4 as an adipokine exerting metabolic effects in glucose metabolism in humans remains uncertain and might be restricted to rodent models.

Effects of transforming growth factor-beta 1 and ascorbic acid on differentiation of human bone-marrow-derived mesenchymal stem cells into smooth muscle cell lineage

Bone-marrow-derived mesenchymal stem cells (MSCs) can differentiate into a variety of cell types including smooth muscle cells (SMCs). We have attempted to demonstrate that, following treatment with transforming growth factor-beta 1 (TGF-beta1) and ascorbic acid (AA), human bone-marrow-derived MSCs differentiate into the SMC lineage for use in tissue engineering. Quantitative polymerase chain reaction for SMC-specific gene (alpha smooth muscle actin, h1-calponin, and SM22alpha) expression was performed on MSCs, which were cultured with various concentrations of TGF-beta1 or AA. TGF-beta1 had a tendency to up-regulate the expression of SMC-specific genes in a dose-dependent manner. The expression of SM22alpha was significantly up-regulated by 30 microM AA. We also investigated the additive effect of TGF-beta1 and AA for differentiation into SMCs and compared this effect with that of other factors including platelet-derived growth factor BB (PDGF-BB). In addition to SMC-specific gene expression, SMC-specific proteins increased by two to four times when TGF-beta1 and AA were used together compared with their administration alone. PDGF did not increase the expression of SMC-specific markers. MSCs cultured with TGF-beta1 and AA did not differentiate into osteoblasts and adipocytes. These results suggest that a combination of TGF-beta1 and AA is useful for the differentiation of MSCs into SMCs for use in tissue engineering.

Retinoic acid receptor gamma activates receptor tyrosine kinase Tie1 gene transcription through transcription factor GATA4 in F9 stem cells

OBJECTIVE

The retinoic acid receptors (RARs) alpha, beta2, and gamma regulate specific subsets of target genes during all-trans retinoic acid (RA) induced differentiation of F9 teratocarcinoma stem cells. The Tie1 gene exhibited reduced expression in RA-treated F9 RARgamma-/- cells as compared to wild-type (WT) by microarray analysis. Our goal was to analyze the Tie1 gene, which encodes a surface receptor tyrosine kinase expressed in the hematovascular system.

MATERIALS AND METHODS

We assessed Tie1, Tie2, Flk1, Runx1, Peg/Mest2, and angiopoietin-1 and 2 mRNA levels and Tie1 promoter activity.

RESULTS

We showed that RARgamma, but not RARalpha or RARbeta2, is required for Tie1 promoter activation by RA. Treatment with a RARgamma selective agonist plus a retinoid X receptor agonist (LGD1069) increased Tie1 mRNA levels by 11- +/- 2.5-fold 48 hours after RA addition in F9 WT, but not in F9 RARgamma-/- cells, by quantitative reverse transcription polymerase chain reaction. Multiple putative GATA elements were identified in the Tie1 proximal promoter. RA increased GATA4 transcripts by 12- +/- 1-fold in F9 WT at 48 hours, but not in F9 RARgamma-/- cells. In addition, transfection of a GATA4 expression vector increased Tie1 promoter/luciferase activity in both RA-treated F9 WT and RARgamma-/- cells. Tie1 promoter deletion analyses indicated that a region of the promoter that possessed multiple GATA sites mediated the RA-associated Tie1 transcriptional increase.

CONCLUSIONS

Our results indicate that GATA4 plays a role in the RA/RARgamma-associated transcriptional activation of the Tie1 promoter. An understanding of RAR specificity in RA signaling should result in insights into hematopoietic stem cell signaling and potentially in improved therapies for several human diseases.

Retinoic acid is a negative regulator of matrix Gla protein gene expression in teleost fish Sparus aurata

Matrix Gla protein (MGP) is an extracellular mineral-binding protein expressed in several tissues while accumulated only in bone and cartilage under physiological conditions. Although the precise molecular mechanism of action of MGP remains unknown, all available evidence indicates that it acts as a physiological inhibitor of mineralization. This work presents the cloning of gilthead seabream MGP gene (SaMGP) and the functional analysis of its promoter. SaMGP gene was found to be organized in five exons and to be under control of a distal and a proximal promoter, both, capable of activating SaMGP transcription in transient transfections. Furthermore, we present strong evidence that retinoic acid down-regulates SaMGP gene transcription by interacting, through binding of its receptor, with a specific region within distal promoter. Interestingly, the presence of repetitive motifs in the proximity of SaMGP gene regulatory regions suggests that they may modulate promoter accessibility to transcription machinery, as already seen for other genes. This work provides additional evidence of the usefulness of non-mammalian model systems to elucidate the complex regulation of MGP gene transcription.

Maternal vitamin A alters gene profiles and structural maturation of the rat ductus arteriosus

Retinoic acid (RA), a metabolite of vitamin A, has been proposed to regulate vascular remodeling and reactivity of the ductus arteriosus (DA). Using rat Affymetrix GeneChips, we found that a considerable number of genes in DA varied their expression levels in accordance with developmental mode: namely, preterm-, term-, and postnatal-dominant clusters. Among a total of 8,740 probe sets, maternal vitamin A administration (MVA) changed the expression levels of 91 genes (116 probe sets) >2.5-fold. About half of preterm- and term-dominant genes responded to MVA, whereas only 5% of postnatal-dominant genes responded to MVA, indicating that fetal-dominant genes were susceptible to RA signals. The expression levels of 51 genes in MVA-treated DA at preterm were similar to the expression levels in nontreated DA at term, indicating that the global gene profile at preterm resembled that of the control animal at term. We observed neointima formation in MVA-treated DA at preterm in accordance with upregulation of fibronectin and hyaluronic acid, whereas it was rarely observed in nontreated DA at preterm. Five fetal cardiac myofibrillar genes were also upregulated in MVA-treated in vivo DA, whereas they were developmentally downregulated in nontreated DA. The present study indicates that MVA-mediated alteration in gene profile was associated with early structural maturation of DA, although MVA-mediated maturation may differ from normal vascular remodeling of DA.

All-trans retinoic acid induces in vitro angiogenesis via retinoic acid receptor: possible involvement of paracrine effects of endogenous vascular endothelial growth factor signaling

A natural retinoid all-trans retinoic acid (ATRA) regulates a variety of important cellular functions via retinoic acid receptor (RAR). ATRA has therapeutically been used against various malignancies including acute promyelocytic leukemia. Recently ATRA has also been recognized to be beneficial against atherosclerotic vascular disorders. However, its effects on angiogenesis remain controversial. We therefore examined ATRA effects on in vitro angiogenesis in terms of capillary-like tube formation using human umbilical vein endothelial cells (HUVECs)/normal human dermal fibroblast (NHDF) coculture. ATRA as well as RAR agonist Am80 significantly induced capillary-like tube formation. The ATRA-induced tube formation was inhibited by coincubation with RAR antagonist LE540/LE135. HUVEC proliferation, but not its migration, was also induced by ATRA. The ATRA-induced tube formation was completely abolished by coincubation with vascular endothelial growth factor (VEGF) neutralizing antibody or with VEGF receptor (VEGFR)-2 (KDR) neutralizing antibody, but not VEGFR-1 (Flt-1) neutralizing antibody. ATRA and Am80 induced VEGF secretion in the coculture as well as VEGF secretion/mRNA expression in NHDFs. Transcription activity of human VEGF gene promoter in NHDFs was stimulated by ATRA, which was augmented by RAR overexpression. ATRA also induced VDGFR-2/KDR mRNA expression in HUVECs. Moreover, ATRA-induced secretion of hepatocyte growth factor as well as angiopoietin-2 in the coculture. Taken together, ATRA may have induced angiogenesis via RAR mainly by stimulation of HUVEC proliferation and enhancement of endogenous VEGF signaling and in part by induction of hepatocyte growth factor and angiopoietin-2 production. Retinoids may therefore be potential candidates for therapeutic angiogenesis against ischemic vascular disorders.

Modulation by the steroid/thyroid hormone superfamily of TGF-beta-stimulated VEGF release from vascular smooth muscle cells

We previously reported that transforming growth factor-beta (TGF-beta) stimulates the release of vascular endothelial growth factor (VEGF) from aortic smooth muscle A10 cells via activation of p38 mitogen-activated protein (MAP) kinase. In the present study, we investigated whether nuclear hormone receptor superfamily members affect TGF-beta-stimulated VEGF release from A10 cells. Retinoic acid or 1,25-dihydroxyvitamin D3 enhanced TGF-beta-induced VEGF release in a concentration-dependent manner, whereas dexamethasone or corticosterone suppressed TGF-beta-induced VEGF release. 1,25-Dihydroxyvitamin D3 and TGF-beta stimulated phosphorylation of p38 MAP kinase in an additive manner. SB203580, an inhibitor of p38 MAP kinase, decreased the VEGF release induced by TGF-beta or 1,25-dihydroxyvitamin D3. However, retinoic acid, dexamethasone, or corticosterone did not affect phosphorylation of p38 MAP kinase. These results indicate that retinoic acid, 1,25-dihydroxyvitamin D3, and glucocorticoids affect TGF-beta-stimulated VEGF release from aortic smooth muscle cells. The stimulatory effect of 1,25-dihydroxyvitamin D3 occurs, in part, via modification of TGF-beta-induced activation of p38 MAP kinase.

Retinoic acid inhibits airway smooth muscle cell migration

Airway remodeling in chronic asthma is characterized by increased smooth muscle mass that is associated with the reduction of the bronchial lumen as well as airway hyperresponsiveness. The development of agents that inhibit smooth muscle growth is therefore of interest for therapy to prevent asthma-associated airway remodeling. All-trans retinoic acid (ATRA) suppresses growth of vascular smooth muscle cells (SMCs) from the systemic and pulmonary circulation. The present study investigated the effects of ATRA on human bronchial (airway) SMCs. Human bronchial SMCs were found to express mRNAs for retinoic acid receptor (RAR)-alpha, -beta, -gamma, and retinoid X receptor (RXR)-alpha, -beta, but not RXR-gamma. Although ATRA was not effective in inhibiting proliferation or in inducing apoptosis in airway SMCs, we found that ATRA (0.2-2 microM) inhibited the SMC migration in response to platelet-derived growth factor (PDGF), as determined in a modified Boyden chamber assay. Both RAR and RXR agonists also blocked PDGF-induced airway SMC migration. ATRA also inhibited PDGF-induced actin reorganization associated with migration. PDGF-induced actin reorganization and migration were blocked by inhibitors of phosphatidylinositol 3 kinase (PI3K) and Akt. However, migration was blocked by inhibitors of the MEK/ERK pathway, with no effect on cytoskeletal reorganization. ATRA suppressed PDGF-induced Akt activation without influencing ERK activation. RAR was found to form protein-protein interactions with the p85 PI3K subunit. These results suggest that retinoic acid inhibits airway SMC migration through the modulation of the PI3K/Akt pathway.

The induction of prostaglandin E synthase and upregulation of cyclooxygenase-2 by 9-cis retinoic acid

9-cis Retinoic acid (9cRA) is a promising lead compound to design the retinoid X receptor (RXR) ligands with the ability to simultaneously activate RXR heterodimers with the selectivity to their nuclear receptor partners. In this study, we investigated the effects of 9cRA on the prostaglandin E2 (PGE2) and thromboxane A2 (TXA2) production. 9cRA increased the PGE2 and TXA2 productions in the presence of lipopolysaccharide (LPS). All-trans retinoic acid, the retinoic acid receptor ligand, also increased their production. We revealed that cyclooxygenase (COX)-2 was clearly induced by 9cRA in the presence of LPS. The induction was not suppressed by indomethacin, which completely inhibited the increase in the LPS-stimulated prostanoid production by 9cRA. The expression levels of the toll-like receptor 4 and CD14, which were components of the LPS receptor complex, were increased by 9cRA in the presence and absence of LPS. PGE synthase was also clearly increased by 9cRA in the presence and absence of LPS. In this study, we noted that 9cRA increased the production of PGE2 and TXA2 by the induction of COX-2 and PGE synthase in the presence of LPS. The induction of the LPS receptor complex by 9cRA is able to upregulate the induction of COX-2 by LPS.

Possible involvement of p44/p42 MAP kinase in retinoic acid-stimulated vascular endothelial growth factor release in aortic smooth muscle cells

Retinoic acid modulates cell growth and differentiation of the vascular system. Vascular endothelial growth factor (VEGF) is known as a vascular permeability factor and a potent mitogen for vascular endothelial cells. In the present study, we investigated whether retinoic acid induces VEGF release in aortic smooth muscle A10 cells and if so, the mechanism of VEGF release. Retinoic acid stimulated VEGF release dose-dependently over the range 0.1 nM-0.1 microM. The retinoic acid-stimulated VEGF release was significantly reduced by actinomycin D. Retinoic acid induced the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase but not p38 MAP kinase or stress-activated protein kinase/c-Jun N-terminal kinase among the MAP kinase superfamily. This effect of retinoic acid was dose-dependent (30 nM-5 microM) and the maximum effect was observed at 0.3 microM. The retinoic acid-stimulated release of VEGF was significantly reduced by PD98059 and U0126, specific MEK inhibitors, which attenuated the retinoic acid-induced phosphorylation of p44/p42 MAP kinase. These results strongly suggest that retinoic acid stimulates the release of VEGF in a p44/p42 MAP kinase-dependent manner in aortic smooth muscle cells.

Comparing genomic and histologic correlations to radiographic changes in tumors: a murine SCC VII model study

RATIONALE AND OBJECTIVES

To investigate the correlation between the temporal changes in T1- and T2-weighted contrast-enhanced magnetic resonance imaging (MRI), histologic evaluation, and genomic analysis using oligonucleotide microarrays in a murine squamous cell carcinoma tumor models.

MATERIALS AND METHODS

The squamous cell carcinoma (SCC VII) cell line was used to initiate subcutaneous tumors in mice. This mouse model has been used as a model for human head and neck carcinomas. Animals were imaged using contrast enhanced MRI (CE-MRI). Different stages of tumor growth were defined based on changes in the T1- and T2-weighted MRI patterns. The contrast enhancing (CE) and nonenhancing (NE) regions of the tumors were marked and biopsied for oligonucleotide microarray and histologic analysis. Tumors with no differential contrast enhancement were used as controls.

RESULTS

Distinct temporal stages of tumor progression can be defined using both T1- and T2-weighted CE-MRI and microarray analysis. The early stage tumors show a homogeneous contrast enhancement pattern in the T1- and T2-weighted images with no significant differential gene expression from the center and periphery of the tumor. The more advanced tumors that show discrete regions of contrast enhancement in the post-contrast T1-weighted MRIs and tissues from the CE and NE regions show distinctly differential gene expression profiles. Histologic analysis (hematoxylin-eosin stain) showed that the samples obtained from the periphery and center of the early stage tumors and the CE and NE regions from these more advanced tumors were similar. The gene expression profiles of late-stage tumors that showed changes in T2-weighted MRI signal intensity were consistent with tissue degradation in the NE region, which also showed characteristic signs of tissue necrosis in histologic analysis.

CONCLUSION

These results show that temporal changes in T1- and T2-weighted CE-MRI are related to distinct gene expression profiles, and histologic analysis may not be sufficient to detect these detailed changes. As tumors progress, discrete regions of post-contrast T1 enhancement are identified; these regions have distinct gene expression patterns despite similar histologic features. In late-stage tumors, regions of T2 signal changes are observed which correspond with tissue necrosis.

Vitamin A and infancy. Biochemical, functional, and clinical aspects

Vitamin A is a very intriguing natural compound. The molecule not only has a complex array of physiological functions, but also represents the precursor of promising and powerful new pharmacological agents. Although several aspects of human retinol metabolism, including absorption and tissue delivery, have been clarified, the type and amounts of vitamin A derivatives that are intracellularly produced remain quite elusive. In addition, their precise function and targets still need to be identified. Retinoic acids, undoubtedly, play a major role in explaining activities of retinol, but, recently, a large number of physiological functions have been attributed to different retinoids and to vitamin A itself. One of the primary roles this vitamin plays is in embryogenesis. Almost all steps in organogenesis are controlled by retinoic acids, thus suggesting that retinol is necessary for proper development of embryonic tissues. These considerations point to the dramatic importance of a sufficient intake of vitamin A and explain the consequences if intake of retinol is deficient. However, hypervitaminosis A also has a number of remarkable negative consequences, which, in same cases, could be fatal. Thus, the use of large doses of retinol in the treatment of some human diseases and the use of megavitamin therapy for certain chronic disorders as well as the growing tendency toward vitamin faddism should alert physicians to the possibility of vitamin overdose.

Regulation of smooth muscle phenotype

Differentiated smooth muscle cells (SMCs) remain highly plastic, enabling them to alter their phenotype in response to environmental and pathologic stimuli. SMCs in vascular pathologies such as atherosclerosis exhibit phenotypes clearly different from those of the mature cells in normal blood vessels. These phenotypically modulated SMCs play an integral role in the development of vascular diseases. This review addresses recent progress in our understanding of the mechanisms that control SMC phenotype during vascular development and in vascular disease. A particular focus is on the transcriptional control programs of the differentiated state of SMCs.

Transcription Suppression of Thromboxane Receptor Gene Expression by Retinoids in Vascular Smooth Muscle Cells

Thromboxane (TX) A2 induces contraction and proliferation of vascular smooth muscle cells (VSMCs) via its specific membrane TX receptor (TXR), possibly leading to the progression of atherosclerosis. Retinoids, derivatives of vitamin A, have recently been shown to be anti-atherosclerotic in VSMCs. We therefore examined the effects of retinoids on TX-induced cell growth and TXR expression in VSMCs. TX-induced VSMC proliferation assessed by 3H-thymidine incorporation was completely abrogated by all-trans retinoic acid (ATRA) treatment. The expression of TXR mRNA was significantly decreased by treatment either with ATRA or its stereoisomer 9-cis retinoic acid (RA). Transcription activity of the TXR gene promoter was suppressed by treatment with these retinoids, and a study using retinoid receptor-selective agonists demonstrated that retinoic acid receptors (RARs), rather than retinoid X receptors (RXRs), were mainly involved in the transcription suppression. Deletion analyses demonstrated that the suppression was mediated via the -22/-7 GC-box related sequence. Electrophoretic mobility shift assays showed that Sp1, but not RAR and/or RXR, could bind to the element. The formation of the Sp1-DNA complex was inhibited by co-incubation with RAR, but not by RXR. Taken together, these findings suggest that TXR gene transcription suppression may be mediated by the inhibition of Sp1 binding to the -22/-7 GC-box related sequence by activated RAR, which may result in the inhibition of TX-induced VSMC proliferation. Our study indicates a novel anti-atherosclerotic action of retinoids in VSMCs.

Retinoic acid binding properties of the lipocalin member beta-lactoglobulin studied by circular dichroism, electronic absorption spectroscopy and molecular modeling methods

Interaction between the Vitamin A derivative all-trans retinoic acid and the lipocalin member bovine beta-lactoglobulin (BLG) was studied by circular dichroism (CD) and electronic absorption spectroscopy at different pH values. In neutral and alkaline solutions achiral retinoic acid forms a non-covalent complex with the protein as indicated by the appearance of a negative Cotton effect around 347 nm associated to the narrowed and red shifted pi-pi(*) absorption band of the ligand. The induced optical activity is attributed to the helical distortion of the conjugated chain caused by the chiral protein binding environment. As the disappearing CD activity showed in the course of CD-pH titration experiment, retinoic acid molecules dissociate from BLG upon acidification but this release is completely reversible as proved by the reconstitution of the CD and absorption spectra after setting the pH back to neutral. This unique behavior of the complex is explained by the conformational change of BLG (Tanford transition) which involves a movement of the EF loop at the entrance of the central cavity from open to closed conformation in the course of pH lowering. From these results it was inferred that retinoic acid binds within the hydrophobic calyx of the beta-barrel.

Origin and differentiation of human and murine stroma

Stromal cells generated in long-term cultures appear to follow a vascular smooth muscle differentiation pathway. Such a pathway, comprising several steps hallmarked by the expression of cytoskeletal and extracellular matrix markers, is found not only for bone marrow stromal cells, but also for stromal cells generated from the different developmental sites of hematopoiesis (yolk sac, aorta-gonad-mesonephros region, fetal liver, and spleen). Factors responsible for this differentiation pathway and its functional significance are discussed. The mesenchymal founder cell might be, at least for bone marrow, a mesenchymal stem cell (MSC), giving rise to stromal cells, endothelial cells, adipocytes, osteoblasts, and chondrocytes. A feature that distinguishes the MSC lineage from that of the hematopoietic stem cell lineage is that differentiation pathways are not strictly delineated, since even apparently fully differentiated cells from a given lineage have the potential to convert into another lineage (phenotype "plasticity") and intermediate cell phenotypes are observed. A stochastic Repression/Induction model that would account for this plasticity is proposed.

Effect of vitamin A deficiency on cardiovascular function in the rat

Selected parameters of cardiovascular function were evaluated in vitamin A-deficient rats at 70 days of age. Resting heart rate was increased by an average of 100 bpm (21.4+/-2.7%), whereas resting systolic blood pressure was normal in vitamin A-deficient animals. The maximal contractile force developed per milligram weight of tissue by aortic rings excised from vitamin A-deficient animals was reduced in response to high potassium (-25.0+/-8.7%) and phorbol 12,13-dibutyrate (-36.8+/-8.4%) but was only slightly reduced in response to norepinephrine (-17.8+/-11.1%). Intimal rubbing to remove the endothelium had no effect on the loss in contractile responsiveness, and the relaxant response to acetylcholine was similar between control and vitamin A-deficient tissue groups. This suggests that the decrease in contractility of vascular smooth muscle from the vitamin A-deficient rats did not involve altered release of endothelium-derived vasoactive factors. Western blot analysis suggested a reduction in the protein levels of several differentiation markers including alpha-actin (-22%), calponin (-37%), desmin (-37%), and vinculin (-40%), whereas the level of PKCalpha was unchanged from control values. Our findings indicate a significant decrease in contractile responsiveness of aortic smooth muscle of the vitamin A-deficient rat that may be associated with a down regulation in the expression of contractile-related proteins.

Cloning of a novel retinoid-inducible serine carboxypeptidase from vascular smooth muscle cells

Retinoids block smooth muscle cell (SMC) proliferation and attenuate neointimal formation after vascular injury, presumably through retinoid receptor-mediated changes in gene expression. To identify target genes in SMC whose encoded proteins could contribute to such favorable biological effects, we performed a subtractive screen for retinoid-inducible genes in cultured SMC. Here, we report on the cloning and initial characterization of a novel retinoid-inducible serine carboxypeptidase (RISC). Expression of RISC is low in cultured SMC but progressively increases over a 5-day time-course treatment with all-trans-retinoic acid. A near full-length rat RISC cDNA was cloned and found to have a 452-amino acid open reading frame containing an amino-terminal signal sequence, followed by several conserved domains comprising the catalytic triad common to members of the serine carboxypeptidase family. In vitro transcription and translation experiments showed that the rat RISC cDNA generates an approximately 51-kDa protein. Confocal immunofluorescence microscopy of COS-7 cells transiently transfected with a RISC-His tag plasmid revealed cytosolic localization of the fusion protein. Western blotting studies using conditioned medium from transfected COS-7 cells suggest that RISC is a secreted protein. Tissue Northern blotting studies demonstrated robust expression of RISC in rat aorta, bladder, and kidney with much lower levels in all other tissues analyzed; high level RISC expression was also observed in human kidney. In situ hybridization verified the localization of RISC to medial SMC of the adult rat aorta. Interestingly, expression in kidney was restricted to proximal convoluted tubules; little or no expression was observed in glomerular cells, distal convoluted and collecting tubules, or medullary cells. Radiation hybrid mapping studies placed the rat RISC locus on chromosome 10q. These studies reveal a novel retinoid-inducible protease whose activity may be involved in vascular wall and kidney homeostasis.

Randomized phase III intergroup trial of isotretinoin to prevent second primary tumors in stage I non-small-cell lung cancer

BACKGROUND

Promising data have suggested that retinoid chemoprevention may help to control second primary tumors (SPTs), recurrence, and mortality of stage I non-small-cell lung cancer (NSCLC) patients.

METHODS

We carried out a National Cancer Institute (NCI) Intergroup phase III trial (NCI #I91-0001) with 1166 patients with pathologic stage I NSCLC (6 weeks to 3 years from definitive resection and no prior radiotherapy or chemotherapy). Patients were randomly assigned to receive a placebo or the retinoid isotretinoin (30 mg/day) for 3 years in a double-blind fashion. Patients were stratified at randomization by tumor stage, histology, and smoking status. The primary endpoint (time to SPT) and the secondary endpoints (times to recurrence and death) were analyzed by log-rank test and the Cox proportional hazards model. All statistical tests were two-sided.

RESULTS

After a median follow-up of 3.5 years, there were no statistically significant differences between the placebo and isotretinoin arms with respect to the time to SPTs, recurrences, or mortality. The unadjusted hazard ratio (HR) of isotretinoin versus placebo was 1.08 (95% confidence interval [CI] = 0.78 to 1.49) for SPTs, 0.99 (95% CI = 0.76 to 1.29) for recurrence, and 1.07 (95% CI = 0.84 to 1.35) for mortality. Multivariate analyses showed that the rate of SPTs was not affected by any stratification factor. Rate of recurrence was affected by tumor stage (HR for T(2) versus T(1) = 1.77 [95% CI = 1.35 to 2.31]) and a treatment-by-smoking interaction (HR for treatment-by-current-versus-never-smoking status = 3.11 [95% CI = 1.00 to 9.71]). Mortality was affected by tumor stage (HR for T(2) versus T(1) = 1.39 [95% CI = 1.10 to 1.77]), histology (HR for squamous versus nonsquamous = 1.31 [95% CI = 1.03 to 1.68]), and a treatment-by-smoking interaction (HR for treatment-by-current-versus-never-smoking = 4.39 [95% CI = 1.11 to 17.29]). Mucocutaneous toxicity (P<.001) and noncompliance (40% versus 25% at 3 years) were higher in the isotretinoin arm than in the placebo arm.

CONCLUSIONS

Isotretinoin treatment did not improve the overall rates of SPTs, recurrences, or mortality in stage I NSCLC. Secondary multivariate and subset analyses suggested that isotretinoin was harmful in current smokers and beneficial in never smokers.

A novel retinoid-response gene set in vascular smooth muscle cells

A modified suppression subtractive hybridization assay was performed to uncover genes induced by all-trans retinoic acid in cultured smooth muscle cells (SMC). Northern blotting studies confirmed the induction of 14 genes, many of which have heretofore been unrecognized as retinoid-inducible. Temporal expression and cycloheximide studies allowed us to categorize these genes as either immediate-early (LOX-1, endolyn, Stoned B/TFIIA alpha/beta-like factor, Src Suppressed C Kinase Substrate, and tissue transglutaminase) or delayed (cathepsin-L, ceruloplasmin, epithelin, importin alpha, alpha(8)-integrin, lactate dehydrogenase B, retinol dehydrogenase, spermidine/spermine N(1)-acetyltransferase, and VCAM-1) retinoid-response genes. A survey of rat tissues showed two of the genes (tissue transglutaminase and alpha(8)-integrin) to be highly restricted to vascular tissue. In situ hybridization verified expression of both tissue transglutaminase and alpha(8)-integrin to SMC in balloon-injured rat carotid artery. These findings unveil a new retinoid-response gene set that should be exploited to define molecular pathways involved in the antagonistic effects of retinoids on SMC growth and neointimal formation.