Insulin-like growth factor-I regulates transcription of the elastin gene through a putative retinoblastoma control element. A role for Sp3 acting as a repressor of elastin gene transcription

Multicenter evaluation of a topical antioxidant serum

BACKGROUND

A new antioxidant serum has been formulated with sodium ascorbate, a sodium salt of Vit C, which aims to address facial photodamage while maintaining a low irritation profile and preserving elastin. Detailed background science has been submitted in a previous publication. This open-label study was conducted to validate the science by demonstrating product efficacy and tolerability in patients with moderate to severe facial photodamage.

METHODS

A multicenter, open-label clinical study was undertaken over 5 months from March 2023 to July 2023. Thirty six eligible participants (35 female, 1 male), aged 38-69 years, and Fitzpatrick skin types II-V were enrolled into and completed the study following 12 weeks of the topical antioxidant serum use twice daily, along with the following supporting products (gentle cleanser, moisturizer, and sunscreen for as needed use). Follow-up visits were conducted in Weeks 2, 4, 8, and 12. At every visit, participants were evaluated for facial photodamage severity and test product tolerability. Additionally, study participants underwent subject assessments and satisfaction questionnaires, investigator assessments, biopsy collection, and photography.

RESULTS

Significant improvements in all evaluated facial photodamage parameters were observed at 12 weeks together with excellent tolerability and subject satisfaction persisting to Week 12 at study completion. Histology most notably revealed increased elastin fibers in 5 out of 5 post 12-week treatment biopsies on Movat staining, while Herovici stains revealed stimulation of collagen and early formation of new fibers.

CONCLUSION

A novel antioxidant serum has demonstrated to be safe and effective for addressing facial photodamage, while stimulating the production of both elastin and collagen in the extracellular matrix (ECM).

Emerging mechanisms of elastin transcriptional regulation

Elastin provides recoil to tissues that stretch such as the lung, blood vessels, and skin. It is deposited in a brief window starting in the prenatal period and extending to adolescence in vertebrates, and then slowly turns over. Elastin insufficiency is seen in conditions such as Williams-Beuren syndrome and elastin-related supravalvar aortic stenosis, which are associated with a range of vascular and connective tissue manifestations. Regulation of the elastin (ELN) gene occurs at multiple levels including promoter activation/inhibition, mRNA stability, interaction with microRNAs, and alternative splicing. However, these mechanisms are incompletely understood. Better understanding of the processes controlling ELN gene expression may improve medicine's ability to intervene in these rare conditions, as well as to replace age-associated losses by re-initiating elastin production. This review describes what is known about the ELN gene promoter structure, transcriptional regulation by cytokines and transcription factors, and posttranscriptional regulation via mRNA stability and micro-RNA and highlights new approaches that may influence regenerative medicine.

Pulse wave velocity is decreased in acromegaly compared to non-acromegaly study participants with similar cardiovascular risk profile

OBJECTIVE

Acromegaly patients were reported to have an increased arterial stiffness that could contribute to the frequent cardiovascular complications in this population. The chronic excess of GH and IGF-1 may lead to arterial stiffening via different mechanisms, including hypertension, impaired glucose tolerance and dyslipidemia, however, it is not known whether the activation of GH/IGF-1 axis might influence arterial stiffening independently of cardiovascular risk factors. The objective of this prospective case-control study was to compare arterial stiffness assessed with pulse-wave velocity (PWV) in acromegaly versus non-acromegaly group with similar cardiovascular risk profile.

DESIGN

This prospective case-control study included 27 patients with active acromegaly, who underwent the assessment of clinical, physiological, biochemical parameters and the evaluation of PWV with applanation tonometry. We used "The epidemiology of cardiovascular disease in different regions of the Russian Federation" study database (n = 522) to establish a non-acromegaly control group with similar cardiovascular risk profile (n = 54). Non-acromegaly control participants underwent the same assessment as acromegaly patients except for the measurement of serum GH and IGF-1 levels. We compared PWV in acromegaly patients to the general non-acromegaly cohort and its subset, matched with acromegaly patients for cardiovascular risk factors. We also investigated the associations of PWV with clinical, physiological and biochemical parameters in acromegaly and non-acromegaly group using correlation and regression analysis with adjustment for age and sex.

RESULTS

Acromegaly patients had lower PWV (6.70 (5.75-7.65) m/s) compared to unmatched non-acromegaly control cohort (7.50 (6.70-8.57) m/s, p = 0.01) and to the non-acromegaly control group matched for cardiovascular risk factors (7.45 (6.73-8.60), p < 0.01). In non-acromegaly control group PWV was associated with BMI (ρ = 0.40, p < 0.01; β = 0.09, p < 0.01), obesity (r = 0.46, p < 0.01; β = 1.36, p < 0.01), systolic blood pressure (ρ = 0.60, p < 0.01; β = 0.05, p < 0.01), diastolic blood pressure (ρ = 0.62, p < 0.01; β = 0.07, p < 0.01), triglycerides (ρ = 0.55, p < 0.01; β = 0.58, p = 0.04), glucose (ρ = 0.54, p < 0.01; β = 0.70, p < 0.01) and diabetes (r = 0.40, p < 0.01; β = 1.10, p = 0.03), while in acromegaly group PWV was associated with IGF-1 expressed in mcg/ml (ρ = -0.49, p ≤0.01; β = -0.002, p ≤0.01) and in percentage of the upper limit of the normal (ρ = -0.47, p = 0.01; β = -0.005, p ≤0.01) as well as with diuretics treatment (β = -1.17, p = 0.03).

CONCLUSIONS

PWV is decreased in acromegaly patients compared to non-acromegaly control participants with similar cardiovascular risk profile. Future studies need to explore the role of GH/IGF-1 axis in the regulation of arterial wall properties and the reliability of PWV as a prognostic marker of cardiovascular complications in acromegaly.

Reduced Frizzled Receptor 4 Expression Prevents WNT/β-Catenin-driven Alveolar Lung Repair in Chronic Obstructive Pulmonary Disease

RATIONALE

Chronic obstructive pulmonary disease (COPD), in particular emphysema, is characterized by loss of parenchymal alveolar tissue and impaired tissue repair. Wingless and INT-1 (WNT)/β-catenin signaling is reduced in COPD; however, the mechanisms thereof, specifically the role of the frizzled (FZD) family of WNT receptors, remain unexplored.

OBJECTIVES

To identify and functionally characterize specific FZD receptors that control downstream WNT signaling in impaired lung repair in COPD.

METHODS

FZD expression was analyzed in lung homogenates and alveolar epithelial type II (ATII) cells of never-smokers, smokers, patients with COPD, and two experimental COPD models by quantitative reverse transcriptase-polymerase chain reaction, immunoblotting, and immunofluorescence. The functional effects of cigarette smoke on FZD4, WNT/β-catenin signaling, and elastogenic components were investigated in primary ATII cells in vitro and in three-dimensional lung tissue cultures ex vivo. Gain- and loss-of-function approaches were applied to determine the effects of FZD4 signaling on alveolar epithelial cell wound healing and repair, as well as on expression of elastogenic components.

MEASUREMENTS AND MAIN RESULTS

FZD4 expression was reduced in human and experimental COPD lung tissues as well as in primary human ATII cells from patients with COPD. Cigarette smoke exposure down-regulated FZD4 expression in vitro and in vivo, along with reduced WNT/β-catenin activity. Inhibition of FZD4 decreased WNT/β-catenin-driven epithelial cell proliferation and wound closure, and it interfered with ATII-to-ATI cell transdifferentiation and organoid formation, which were augmented by FZD4 overexpression. Moreover, FZD4 restoration by overexpression or pharmacological induction led to induction of WNT/β-catenin signaling and expression of elastogenic components in three-dimensional lung tissue cultures ex vivo.

CONCLUSIONS

Reduced FZD4 expression in COPD contributes to impaired alveolar repair capacity.

Transcriptional and posttranscriptional mechanisms contribute to the dysregulation of elastogenesis in Schimke immuno-osseous dysplasia

BACKGROUND

Schimke immuno-osseous dysplasia (SIOD) is an autosomal recessive disorder caused by mutations in SMARCAL1. A frequent complication is arteriosclerosis associated with reduced elastin expression; however, the mechanism underlying the reduced elastin expression remains unknown.

METHODS

Expression of transcriptional regulators of elastin (ELN) and microRNA (miRNA) regulators of ELN messenger RNA (mRNA), ELN promoter methylation, and ELN mRNA poly(A) tail length were assessed by quantitative RT-PCR, bisulfite Sanger sequencing, and the Poly(A) Tail Length Assay Kit, respectively, in unaffected developing human aortae and in an SIOD aorta.

RESULTS

Comparing unaffected fetal and adult aortae, ELN precursor mRNA (pre-mRNA) levels remained nearly constant, whereas mRNA levels declined by ~10(2)-fold. This corresponded with a reduction in poly(A) tail length but not with changes in the other parameters. In contrast, compared to the unaffected fetal aortae, the SIOD aorta had 18-fold less ELN pre-mRNA and 10(4)-fold less mRNA. This corresponded with increased expression of miRNA regulators and shorter ELN mRNA poly(A) tail lengths but not with altered expression of ELN transcriptional regulators or ELN promoter methylation.

CONCLUSION

Posttranscriptional mechanisms account for the reduction in ELN mRNA levels in unaffected aortae, whereas transcriptional and posttranscriptional mechanisms reduce elastin expression in SIOD aorta and predispose to arteriosclerosis.

Synthetic ligands of the elastin receptor induce elastogenesis in human dermal fibroblasts via activation of their IGF-1 receptors

BACKGROUND

We have previously reported that a mixture of peptides obtained after chemical or enzymatic degradation of bovine elastin, induced new elastogenesis in human skin.

OBJECTIVE

Now, we investigated the elastogenic potential of synthetic peptides mimicking the elastin-derived, VGVAPG sequence, IGVAPG sequence that we found in the rice bran, and a similar peptide, VGVTAG that we identified in the IGF-1-binding protein-1 (IGFBP-1).

RESULTS

We now demonstrate that treatment with each of these xGVxxG peptides (recognizable by the anti-elastin antibody), up-regulated the levels of elastin-encoding mRNA, tropoelastin protein, and the deposition of new elastic fibers in cultures of human dermal fibroblasts and in cultured explants of human skin. Importantly, we found that such induction of new elastogenesis may involve two parallel signaling pathways triggered after activation of IGF-1 receptor. In the first one, the xGVxxG peptides interact with the cell surface elastin receptor, thereby causing the downstream activation of the c-Src kinase and a consequent cross-activation of the adjacent IGF-1R, even in the absence of its principal ligand. In the second pathway their hydrophobic association with the N-terminal domain (VGVTAG) of the serum-derived IGFBP-1 induces conformational changes of this IGF-1 chaperone allowing for the release of its cargo and a consequent ligand-specific phosphorylation of IGF-1R.

CONCLUSION

We present a novel, clinically relevant mechanism in which products of partial degradation of dermal elastin may stimulate production of new elastic fibers by dermal fibroblasts. Our findings particularly encourage the use of biologically safe synthetic xGVxxG peptides for regeneration of the injured or aged human skin.

NADPH Oxidase Activity in Cerebral Arterioles Is a Key Mediator of Cerebral Small Vessel Disease-Implications for Prevention

Cerebral small vessel disease (SVD), a common feature of brain aging, is characterized by lacunar infarcts, microbleeds, leukoaraiosis, and a leaky blood-brain barrier. Functionally, it is associated with cognitive decline, dementia, depression, gait abnormalities, and increased risk for stroke. Cerebral arterioles in this syndrome tend to hypertrophy and lose their capacity for adaptive vasodilation. Rodent studies strongly suggest that activation of Nox2-dependent NADPH oxidase activity is a crucial driver of these structural and functional derangements of cerebral arterioles, in part owing to impairment of endothelial nitric oxide synthase (eNOS) activity. This oxidative stress may also contribute to the breakdown of the blood-brain barrier seen in SVD. Hypertension, aging, metabolic syndrome, smoking, hyperglycemia, and elevated homocysteine may promote activation of NADPH oxidase in cerebral arterioles. Inhibition of NADPH oxidase with phycocyanobilin from spirulina, as well as high-dose statin therapy, may have potential for prevention and control of SVD, and high-potassium diets merit study in this regard. Measures which support effective eNOS activity in other ways-exercise training, supplemental citrulline, certain dietary flavonoids (as in cocoa and green tea), and capsaicin, may also improve the function of cerebral arterioles. Asian epidemiology suggests that increased protein intakes may decrease risk for SVD; conceivably, arginine and/or cysteine-which boosts tissue glutathione synthesis, and can be administered as N-acetylcysteine-mediate this benefit. Ameliorating the risk factors for SVD-including hypertension, metabolic syndrome, hyperglycemia, smoking, and elevated homocysteine-also may help to prevent and control this syndrome, although few clinical trials have addressed this issue to date.

Sodium L-ascorbate enhances elastic fibers deposition by fibroblasts from normal and pathologic human skin

BACKGROUND

Vitamin C (L-ascorbic acid), a known enhancer of collagen deposition, has also been identified as an inhibitor of elastogenesis.

OBJECTIVE

Present studies explored whether and how the L-ascorbic acid derivative (+) sodium L-ascorbate (SA) would affect production of collagen and elastic fibers in cultures of fibroblasts derived from normal human skin and dermal fat, as well as in explants of normal human skin, stretch-marked skin and keloids.

METHODS

Effects of SA on the extracellular matrix production were assessed quantitatively by PCR analyses, western blots, biochemical assay of insoluble elastin and by immuno-histochemistry. We also evaluated effects of SA on production of the reactive oxygen species (ROS) and phosphorylation of IGF-I and insulin receptors.

RESULTS

SA, applied in 50-200 μM concentrations, stimulates production of both collagen and elastic fibers in all tested cultures. Moreover, combination of SA with a proline hydroxylase inhibitor induces a beneficial remodelling in explants of dermal scars, resulting in the inhibition of collagen deposition and induction of new elastogenesis. Importantly, we revealed that SA stimulates elastogenesis only after intracellular influx of non-oxidized ascorbate anions (facilitated by the sodium-dependent ascorbate transporter), that causes reduction of intracellular ROS, activation of c-Src tyrosine kinase and the enhancement of IGF-1-induced phosphorylation of the IGF-1 receptor that ultimately triggers elastogenic signalling pathway.

CONCLUSION

Our results endorse the use of this potent stimulator of collagen and elastin production in the treatment of wrinkled and stretch-marked skin. They also encourage inclusion of SA into therapeutic combinations with collagenogenesis inhibitors to prevent formation of dermal scars and keloids.

Perspectives on stem cell-based elastic matrix regenerative therapies for abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are potentially fatal conditions that are characterized by decreased flexibility of the aortic wall due to proteolytic loss of the structural matrix. This leads to their gradual weakening and ultimate rupture. Drug-based inhibition of proteolytic enzymes may provide a nonsurgical treatment alternative for growing AAAs, although it might at best be sufficient to slow their growth. Regenerative repair of disrupted elastic matrix is required if regression of AAAs to a healthy state is to be achieved. Terminally differentiated adult and diseased vascular cells are poorly capable of affecting such regenerative repair. In this context, stem cells and their smooth muscle cell-like derivatives may represent alternate cell sources for regenerative AAA cell therapies. This article examines the pros and cons of using different autologous stem cell sources for AAA therapy, the requirements they must fulfill to provide therapeutic benefit, and the current progress toward characterizing the cells' ability to synthesize elastin, assemble elastic matrix structures, and influence the regenerative potential of diseased vascular cell types. The article also provides a detailed perspective on the limitations, uncertainties, and challenges that will need to be overcome or circumvented to translate current strategies for stem cell use into clinically viable AAA therapies. These therapies will provide a much needed nonsurgical treatment option for the rapidly growing, high-risk, and vulnerable elderly demographic.

A cytokine axis regulates elastin formation and degradation

Underlying the dynamic regulation of tropoelastin expression and elastin formation in development and disease are transcriptional and post-transcriptional mechanisms that have been the focus of much research. Of particular importance is the cytokine-governed elastin regulatory axis in which the pro-elastogenic activities of transforming growth factor β-1 (TGFβ1) and insulin-like growth factor-I (IGF-I) are opposed by anti-elastogenic activities of basic fibroblast growth factor (bFGF/FGF-2), heparin-binding epidermal growth factor-like growth factor (HB-EGF), EGF, PDGF-BB, TGFα, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β and noncanonical TGFβ1 signaling. A key mechanistic feature of the regulatory axis is that cytokines influence elastin formation through effects on the cell cycle involving control of cyclin-cyclin dependent kinase complexes and activation of the Ras/MEK/ERK signaling pathway. In this article we provide an overview of the major cytokines/growth factors that modulate elastogenesis and describe the underlying molecular mechanisms for their action on elastin production.

Insulin induces production of new elastin in cultures of human aortic smooth muscle cells

Diabetes mellitus accelerates atherosclerotic progression, peripheral angiopathy development, and arterial hypertension, all of which are associated with elastic fiber disease. However, the potential mechanistic links between insulin deficiency and impaired elastogenesis in diabetes have not been explored. Results of the present study reveal that insulin administered in therapeutically relevant concentrations (0.5 to 10 nmol/L) selectively stimulates formation of new elastic fibers in cultures of human aortic smooth muscle cells. These concentrations of insulin neither up-regulate collagen type I and fibronectin deposition nor stimulate cellular proliferation. Further, the elastogenic effect of insulin occurs after insulin receptor activation, which triggers the PI3K downstream signaling pathway and activates elastin gene transcription. In addition, the promoter region of the human elastin gene contains the CAAATAA sequence, consistent with the FoxO-recognized element, and the genomic effects of insulin occur after removal of the FoxO1 transcriptional inhibitor from the FoxO-recognized element in the elastin gene promoter. In addition, insulin signaling facilitates the association of tropoelastin with its specific 67-kDa elastin-binding protein/spliced form of β-galactosidase chaperone, enhancing secretion. These results are crucial to understanding of the molecular and cellular mechanisms of diabetes-associated vascular disease, and, in particular, endorse use of insulin therapy for treatment of atherosclerotic lesions in patients with type 1 diabetes, in which induction of new elastic fibers would mechanically stabilize the developing plaques and prevent arterial occlusions.

Retinoblastoma protein modulates the inverse relationship between cellular proliferation and elastogenesis

The mechanism that leads to the inverse relationship between heightened cellular proliferation and the cessation of elastic fibers production, observed during formation of the arterial occlusions and dermal scars, is not fully understood. Because the retinoblastoma protein (Rb), responsible for cell cycle initiation, has also been implicated in insulin-like growth factor-I-mediated signaling stimulating elastin gene activation, we explored whether differential phosphorylation of Rb by various cyclin·cyclin-dependent kinase complexes would be responsible for promoting either elastogenic or pro-proliferative signals. We first tested cultures of dermal fibroblasts derived from Costello syndrome patients, in which heightened proliferation driven by mutated oncogenic H-Ras coincides with inhibition of elastogenesis. We found that Costello syndrome fibroblasts display elevated level of Rb phosphorylation on serine 780 (Ser(P)-780-Rb) and that pharmacological inhibition of Ras with radicicol, Mek/Erk with PD98059, or cyclin-dependent kinase 4 with PD0332991 not only leads to down-regulation of Ser(P)-780-Rb levels but also enhances Rb phosphorylation on threonine-821 (Thr(P)-821-Rb), which coincides with the recovery of elastin production. Then we demonstrated that treatment of normal skin fibroblasts with the pro-proliferative PDGF BB also up-regulates Ser(P)-780-Rb levels, but treatment with the pro-elastogenic insulin-like growth factor-I activates cyclinE-cdk2 complex to phosphorylate Rb on Thr-821. Importantly, we have established that elevation of Thr(P)-821-Rb promotes Rb binding to the Sp1 transcription factor and that successive binding of the Rb-Sp1 complex to the retinoblastoma control element within the elastin gene promoter stimulates tropoelastin transcription. In summary, we provide novel insight into the role of Rb in mediating the inverse relationship between elastogenesis and cellular proliferation.

Intravenous and intramyocardial injection of apoptotic white blood cell suspensions prevents ventricular remodelling by increasing elastin expression in cardiac scar tissue after myocardial infarction

Congestive heart failure developing after acute myocardial infarction (AMI) is a major cause of morbidity and mortality. Clinical trials of cell-based therapy after AMI evidenced only a moderate benefit. We could show previously that suspensions of apoptotic peripheral blood mononuclear cells (PBMC) are able to reduce myocardial damage in a rat model of AMI. Here we experimentally examined the biochemical mechanisms involved in preventing ventricular remodelling and preserving cardiac function after AMI. Cell suspensions of apoptotic cells were injected intravenously or intramyocardially after experimental AMI induced by coronary artery ligation in rats. Administration of cell culture medium or viable PBMC served as controls. Immunohistological analysis was performed to analyse the cellular infiltrate in the ischaemic myocardium. Cardiac function was quantified by echocardiography. Planimetry of the infarcted hearts showed a significant reduction of infarction size and an improvement of post AMI remodelling in rats treated with suspensions of apoptotic PBMC (injected either intravenously or intramoycardially). Moreover, these hearts evidenced enhanced homing of macrophages and cells staining positive for c-kit, FLK-1, IGF-I and FGF-2 as compared to controls. A major finding in this study further was that the ratio of elastic and collagenous fibres within the scar tissue was altered in a favourable fashion in rats injected with apoptotic cells. Intravenous or intramyocardial injection of apoptotic cell suspensions results in attenuation of myocardial remodelling after experimental AMI, preserves left ventricular function, increases homing of regenerative cells and alters the composition of cardiac scar tissue. The higher expression of elastic fibres provides passive energy to the cardiac scar tissue and results in prevention of ventricular remodelling.

A doxycycline loaded, controlled-release, biodegradable fiber for the treatment of aortic aneurysms

The pathogenesis of aortic aneurysm (AA) is characterized by degradation of extracellular matrix with increased matrix metalloproteinases (MMPs) and inflammatory reaction. Doxycycline (DOXY) has been reported to control the extension of AA by regulation of MMP. However, systemic administration may cause adverse side effects. In this study, we demonstrated the possibility of local administration of DOXY controlled-release biodegradable fiber (DCRBF) for AA in mice. DCRBF was fabricated by biodegradable polymer (polylactic acid; PLA) mixed with DOXY using an electrospinning technique. DCRBF was cocultured with SMCs, macrophages and aortic tissue, and placed on an abdominal aortic aneurysm which induced apolipoprotein E-deficient mice. We evaluated gene and protein expression of proteases, elastin and inflammatory markers. In the presence of DCRBF, MMP-12 was significantly decreased, TGF-β1 and Lox were significantly increased in SMC gene expression, MMP-9 and -12 significantly decreased gene expression of macrophages. The DCRBF preserved elastin content and decreased MMP-2 and -9 in aortic tissue. In addition, IGF-1 and TIMP-1 were significantly increased and IL-6 and TNF-α were significantly decreased with DCRBF in vivo. In conclusion, our results suggested that local administration of DCRBF may become a promising alternative therapeutic strategy for AA.

Epigenetic silencing of lysyl oxidase-like-1 through DNA hypermethylation in an autosomal recessive cutis laxa case

We have recently reported a case of cutis laxa caused by a fibulin-5 missense mutation (p.C217R). Skin fibroblasts from this individual showed an abnormal pattern of expression of several genes coding for elastic fiber-related proteins, including lysyl oxidase-like-1 (LOXL1). In this study we intended to elucidate the mechanism responsible for LOXL1 downregulation in these fibulin-5-mutant cells. We identified a proximal region (-442/-342) of the human LOXL1 promoter in which two binding sites for the transcription factor specific protein 1 (Sp-1) are required for gene activity in normal fibroblasts. Binding of Sp-1 to these sequences was dramatically reduced within cutis laxa cells, although Sp-1 expression was normal. Further analysis of the promoter sequence found increased methylation levels in cutis laxa cells compared with cells from unaffected individuals. When DNA methyltransferase activity was transiently inhibited in cutis laxa cells using the 5-aza-2'-deoxycytidine, we found a significant increase in LOXL1 expression. In conclusion, besides changes caused by the fibulin-5 mutation, LOXL1 gene regulation is affected by an epigenetic mechanism that can be reversed by an inhibitor of DNA methyltransferase activity. It is not yet known whether LOXL1 gene expression is affected in all cases of cutis laxa arising from fibulin-5 mutation.

Transcription of human resistin gene involves an interaction of Sp1 with peroxisome proliferator-activating receptor gamma (PPARgamma)

BACKGROUND

Resistin is a cysteine rich protein, mainly expressed and secreted by circulating human mononuclear cells. While several factors responsible for transcription of mouse resistin gene have been identified, not much is known about the factors responsible for the differential expression of human resistin.

METHODOLOGY/PRINCIPAL FINDING

We show that the minimal promoter of human resistin lies within approximately 80 bp sequence upstream of the transcriptional start site (-240) whereas binding sites for cRel, CCAAT enhancer binding protein alpha (C/EBP-alpha), activating transcription factor 2 (ATF-2) and activator protein 1 (AP-1) transcription factors, important for induced expression, are present within sequences up to -619. Specificity Protein 1(Sp1) binding site (-276 to -295) is also present and an interaction of Sp1 with peroxisome proliferator activating receptor gamma (PPARgamma) is necessary for constitutive expression in U937 cells. Indeed co-immunoprecipitation assay demonstrated a direct physical interaction of Sp1 with PPARgamma in whole cell extracts of U937 cells. Phorbol myristate acetate (PMA) upregulated the expression of resistin mRNA in U937 cells by increasing the recruitment of Sp1, ATF-2 and PPARgamma on the resistin gene promoter. Furthermore, PMA stimulation of U937 cells resulted in the disruption of Sp1 and PPARgamma interaction. Chromatin immunoprecipitation (ChIP) assay confirmed the recruitment of transcription factors phospho ATF-2, Sp1, Sp3, PPARgamma, chromatin modifier histone deacetylase 1 (HDAC1) and the acetylated form of histone H3 but not cRel, C/EBP-alpha and phospho c-Jun during resistin gene transcription.

CONCLUSION

Our findings suggest a complex interplay of Sp1 and PPARgamma along with other transcription factors that drives the expression of resistin in human monocytic U937 cells.

Fibroblast growth factor receptors control epithelial-mesenchymal interactions necessary for alveolar elastogenesis

RATIONALE

The mechanisms contributing to alveolar formation are poorly understood. A better understanding of these processes will improve efforts to ameliorate lung disease of the newborn and promote alveolar repair in the adult. Previous studies have identified impaired alveogenesis in mice bearing compound mutations of fibroblast growth factor (FGF) receptors (FGFRs) 3 and 4, indicating that these receptors cooperatively promote postnatal alveolar formation.

OBJECTIVES

To determine the molecular and cellular mechanisms of FGF-mediated alveolar formation.

METHODS

Compound FGFR3/FGFR4-deficient mice were assessed for temporal changes in lung growth, airspace morphometry, and genome-wide expression. Observed gene expression changes were validated using quantitative real-time RT-PCR, tissue biochemistry, histochemistry, and ELISA. Autocrine and paracrine regulatory mechanisms were investigated using isolated lung mesenchymal cells and type II pneumocytes.

MEASUREMENTS AND MAIN RESULTS

Quantitative analysis of airspace ontogeny confirmed a failure of secondary crest elongation in compound mutant mice. Genome-wide expression profiling identified molecular alterations in these mice involving aberrant expression of numerous extracellular matrix molecules. Biochemical and histochemical analysis confirmed changes in elastic fiber gene expression resulted in temporal increases in elastin deposition with the loss of typical spatial restriction. No abnormalities in elastic fiber gene expression were observed in isolated mesenchymal cells, indicating that abnormal elastogenesis in compound mutant mice is not cell autonomous. Increased expression of paracrine factors, including insulin-like growth factor-1, in freshly-isolated type II pneumocytes indicated that these cells contribute to the observed pathology.

CONCLUSIONS

Epithelial/mesenchymal signaling mechanisms appear to contribute to FGFR-dependent alveolar elastogenesis and proper airspace formation.

Aldosterone stimulates elastogenesis in cardiac fibroblasts via mineralocorticoid receptor-independent action involving the consecutive activation of Galpha13, c-Src, the insulin-like growth factor-I receptor, and phosphatidylinositol 3-kinase/Akt

We previously demonstrated that aldosterone, which stimulates collagen production through the mineralocorticoid receptor (MR)-dependent pathway, also induces elastogenesis via a parallel MR-independent mechanism involving insulin-like growth factor-I receptor (IGF-IR) signaling. The present study provides a more detailed explanation of this signaling pathway. Our data demonstrate that small interfering RNA-driven elimination of MR in cardiac fibroblasts does not inhibit aldosterone-induced IGF-IR phosphorylation and subsequent increase in elastin production. These results exclude the involvement of the MR in aldosterone-induced increases in elastin production. Results of further experiments aimed at identifying the upstream signaling component(s) that might be activated by aldosterone also eliminate the putative involvement of pertussis toxin-sensitive Galphai proteins, which have previously been shown to be responsible for some MR-independent effects of aldosterone. Instead, we found that small interfering RNA-dependent elimination of another heterotrimeric G protein, Galpha13, eliminates aldosterone-induced elastogenesis. We further demonstrate that aldosterone first engages Galpha13 and then promotes its transient interaction with c-Src, which constitutes a prerequisite step for aldosterone-dependent activation of the IGF-IR and propagation of consecutive downstream elastogenic signaling involving phosphatidylinositol 3-kinase/Akt. In summary, the data we present reveal new details of an MR-independent cellular signaling pathway through which aldosterone stimulates elastogenesis in human cardiac fibroblasts.

IGF system and peripheral arterial disease: relationship with disease severity and inflammatory status of the affected limb

OBJECTIVES

IGF-1 and its binding proteins are involved in the pathogenesis of atherosclerosis. We designed this study to unravel the relationship of the IGF system with peripheral arterial disease (PAD).

DESIGN

Case-control, cross-sectional study.

MEASUREMENTS

Serum levels of IGF-1, IGFBP-3 and acid labile subunit (ALS) were measured in 96 PAD patients and 89 controls. In 28 patients who underwent peripheral angiography, C-reactive protein (CRP), IGF-1, IGFBP-3 and ALS were measured in blood from femoral vein of the affected limb and aorta.

RESULTS

Compared to controls, PAD patients showed lower levels of IGFBP-3 (3569 +/- 115 vs. 3106 +/- 107 microg/l, P < 0.01), and ALS (12.2 +/- 0.5 vs. 8.3 +/- 0.5 mg/l, P < 0.01). In PAD, concentrations of IGFBP-3 and ALS were significantly lower in patients with ankle/brachial index less than median than in those with a less severe PAD. In the affected limb, CRP venous-arterial difference correlated negatively with that of IGF-1 (rho = -0.57, P < 0.01), and positively with that of IGFBP-3 (rho = 0.63, P < 0.01). At multivariate analysis, a high transfemoral gradient of CRP was independently associated with a low transfemoral gradient of IGF-1 (beta coefficient = -0.48, P < 0.01), and a high transfemoral gradient of IGFBP-3 (beta coefficient = 0.22, P < 0.05).

CONCLUSIONS

This study is the first to demonstrate that the systemic levels of IGF axis components are associated with the presence and severity of PAD, and that the inflammatory status of the ischaemic limb affects the transfemoral concentrations of IGF-1 and IGFBP-3. Due to the importance of IGF axis in modulating atherosclerotic plaque progression, our data may contribute to a better understanding of PAD pathophysiology.

Insulin-like growth factor-1 receptor polymorphism and ischemic stroke: a case-control study in Chinese population

OBJECTIVES

Low levels of insulin-like growth factor 1 (IGF-1) are associated with atherosclerosis, and insulin-like growth factor-1 receptor (IGF-1R) polymorphisms can change plasma levels of IGF-1 and may alter the function of the receptor. Whether there is any association of genetic variation in IGF-1R gene with ischemic stroke (IS) is presently unknown.

MATERIALS AND METHOD

A 1:1 case-control study was conducted. The G --> A polymorphism of IGF-1R gene (rs2229765) were analyzed by TaqMan SNP genotyping technique in Chinese patients with IS (n = 309) and old subjects without IS (n = 309).

RESULTS

The frequency of A allele in the patients and controls was 45.79% and 39.64%, respectively. The AA genotype distribution of IGF-1R gene was significantly higher in the patients (27.51%) than controls (18.23%; P = 0.022). Conditional logistic regression revealed that the AA genotype of IGF-1R was associated with IS (OR = 1.641, P = 0.022). After adjustment for smoking, alcohol drinking, history of hypertension, and body mass index, IGF-1R AA genotype was still significantly associated with an increased risk of IS (OR = 1.787, P = 0.029), compared with IGF-1R GG.

CONCLUSIONS

The G --> A polymorphism in IGF-1R gene may affect the susceptibility to IS in Chinese population.

Effects of trichostatin A on neuronal mu-opioid receptor gene expression

In this study, we determined the effects of a histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), on neuronal mu-opioid receptor (MOR) gene expression using human neuronal NMB cells, endogenously expressing MOR. Recruitment of two classes of HDAC, HDAC1 and HDAC2, to MOR promoter region in situ was detected via chromatin immunoprecipitation (ChIP) analysis with NMB cells. Functional analysis using the luciferase reporter gene system showed that TSA induced an approximately 3-fold increase of the promoter activity as compared to the vehicle treated group. Mutation analysis demonstrated that TSA response was mediated by both dsDNA (Sp1/Sp3 binding site) and ssDNA (PolyC binding protein1, PCBP, binding site) elements located in mouse MOR proximal core promoter region, further suggesting the functional importance of this cis-element, which shows high sequence homology between human and mouse MOR genes. ChIP analysis further suggested that TSA enhanced the recruitment of Sp1/Sp3 and PCBP to the promoter region, whereas no significant changes of total proteins were observed in response to TSA using Western blot analysis. Moreover, confocal images showed TSA-induced nuclear hot spots of endogenous PCBP in neuronal cells, whereas no obvious nuclear PCBP hotspot was observed in vehicle treated cells. Taken together, these results suggested that TSA enhanced neuronal MOR gene expression at the transcriptional level. RT-PCR analysis further revealed that TSA also decreased the steady-state level of MOR mRNA in a time-dependent manner by enhancing its instability. Thus, data suggest that TSA, an epigenetic regulator, affects neuronal MOR gene expression at both transcriptional and post-transcriptional levels.

Aldosterone induces elastin production in cardiac fibroblasts through activation of insulin-like growth factor-I receptors in a mineralocorticoid receptor-independent manner

Aldosterone is known to regulate electrolyte homeostasis, but it may also contribute to other processes, including the maladaptive remodeling of postinfarct hearts. Because aldosterone has been implicated in the stimulation of collagen production in the heart, we investigated whether it would also affect elastin deposition in cultures of human cardiac fibroblasts. We first demonstrated that treatment with 1 to 50 nmol/L aldosterone leads to a significant increase in collagen type I mRNA levels and in subsequent collagen fiber deposition. Pretreatment of cells with the mineralocorticoid receptor antagonist spironolactone, but not with the glucocorticoid receptor antagonist RU 486, inhibited collagen synthesis in aldosterone-treated cultures. Most importantly, we demonstrated that aldosterone also increases elastin mRNA levels, tropoelastin synthesis, and elastic fiber deposition in a dose-dependent manner. Strikingly, neither spironolactone nor RU 486 eliminated aldosterone-induced increases in elastin production. We further discovered that the proelastogenic effect of aldosterone involves a rapid increase in tyrosine phosphorylation of the insulin-like growth factor-I receptor and that the insulin-like growth factor-I receptor kinase inhibitor AG1024 or an anti-insulin-like growth factor-I receptor-neutralizing antibody inhibits both insulin-like growth factor-I and aldosterone-induced elastogenesis. Thus, we have demonstrated for the first time that aldosterone, which stimulates collagen production through the mineralocorticoid receptor-dependent pathway, also increases elastogenesis via a parallel mineralocorticoid receptor-independent pathway involving I insulin-like growth factor-I receptor signaling.

Down-regulation of human topoisomerase IIalpha expression correlates with relative amounts of specificity factors Sp1 and Sp3 bound at proximal and distal promoter regions

Background

Topoisomerase IIα has been shown to be down-regulated in doxorubicin-resistant cell lines. The specificity proteins Sp1 and Sp3 have been implicated in regulation of topoisomerase IIα transcription, although the mechanism by which they regulate expression is not fully understood. Sp1 has been shown to bind specifically to both proximal and distal GC elements of the human topoisomerase IIα promoter in vitro, while Sp3 binds only to the distal GC element unless additional flanking sequences are included. While Sp1 is thought to be an activator of human topoisomerase IIα, the functional significance of Sp3 binding is not known. Therefore, we sought to determine the functional relationship between Sp1 and Sp3 binding to the topoisomerase IIα promoter in vivo. We investigated endogenous levels of Sp1, Sp3 and topoisomerase IIα as well as binding of both Sp1 and Sp3 to the GC boxes of the topoisomerase IIα promoter in breast cancer cell lines in vivo after short term doxorubicin exposure.

Results

Functional effects of Sp1 and Sp3 were studied using transient cotransfection assays using a topoisomerase IIα promoter reporter construct. The in vivo interactions of Sp1 and Sp3 with the GC elements of the topoisomerase IIα promoter were studied in doxorubicin-treated breast cancer cell lines using chromatin immunoprecipitation assays. Relative amounts of endogenous proteins were measured using immunoblotting. In vivo DNA looping mediated by proteins bound at the GC1 and GC2 elements was studied using the chromatin conformation capture assay. Both Sp1 and Sp3 bound to the GC1 and GC2 regions. Sp1 and Sp3 were transcriptional activators and repressors respectively, with Sp3 repression being dominant over Sp1-mediated activation. The GC1 and GC2 elements are linked in vivo to form a loop, thus bringing distal regulatory elements and their cognate transcription factors into close proximity with the transcription start site.

Conclusion

These observations provide a mechanistic explanation for the modulation of topoisomerase IIα and concomitant down-regulation that can be mediated by topoisomerase II poisons. Competition between Sp1 and Sp3 for the same cognate DNA would result in activation or repression depending on absolute amounts of each transcription factor in cells treated with doxorubicin.

Activation of elastin transcription by transforming growth factor-beta in human lung fibroblasts

Elastin synthesis is essential for lung development and postnatal maturation as well as for repair following injury. Using human embryonic lung fibroblasts that express undetectable levels of elastin as assessed by Northern analyses, we found that treatment with exogenous transforming growth factor-beta (TGF-beta) induced rapid and transient increases in levels of elastin heterogeneous nuclear RNA (hnRNA) followed by increases of elastin mRNA and protein expression. In fibroblasts derived from transgenic mice, TGF-beta induced increases in the expression of a human elastin gene promoter fragment driving a chloramphenicol acetyl transferase reporter gene. The induction of elastin hnRNA and mRNA expression by TGF-beta was abolished by pretreatments with TGF-beta receptor I inhibitor, global transcription inhibitor actinomycin D, and partially blocked by addition of protein synthesis inhibitor cycloheximide, but was not affected by the p44/42 MAPK inhibitor U0126. Pretreatment with the p38 MAPK inhibitor SB-203580 also partially attenuated the levels of TGF-beta-induced elastin mRNA but not its hnRNA. Western analysis indicated that TGF-beta stimulated Akt phosphorylation. Inhibition of phosphatidylinositol 3-kinase and Akt phosphorylation by LY-294002 abolished TGF-beta-induced increases in elastin hnRNA and mRNA expression. Treatment of lung fibroblasts with interleukin-1beta or the histone deacetylase inhibitor trichostatin A inhibited TGF-beta-induced elastin mRNA and hnRNA expression by a mechanism that involved inhibition of Akt phosphorylation. Downregulation of Akt2 but not Akt1 expression employing small interfering RNA duplexes blocked TGF-beta-induced increases of elastin hnRNA and mRNA levels. Together, our results demonstrated that TGF-beta activates elastin transcription that is dependent on phosphatidylinositol 3-kinase/Akt activity.

Positive transcriptional regulatory element located within exon 1 of elastin gene

Elastin gene transcription is cell type specific and developmentally regulated, but the promoter often exhibits relatively weak activity in transient transfections of cells that express elastin at high levels. To search for positive-acting regulatory sequences, we isolated genomic clones spanning the mouse elastin gene and extensive 5'- and 3'-flanking regions. Restriction fragments of potential regulatory regions were ligated 5' or 3' relative to the active promoter to test for enhancer activity in transient transfections of fetal rat lung fibroblasts, which express elastin at high levels, and distal lung epithelial cells, which do not express detectable elastin. Fragments of intron 1 did not exhibit significant enhancer activity. Inclusion of the 84-bp exon 1 and adjacent 5'-untranslated region increased activity of the elastin promoter approximately sixfold compared with parental constructs. Transfections with constructs of varying promoter length showed that as little as 40 bp of the 5' end of exon 1 confers enhanced activity in elastin-expressing rat lung fibroblasts, but these constructs had variable activity in lung epithelial cell lines. This region, localized between the transcription start site and extending into exon 1, binds Sp1 in nuclear extracts from elastin-expressing cells. These studies indicate a role for the 5' end of the first exon of the elastin gene in regulating strong transcriptional activity in elastogenic cells.

Interleukin-1β Increases Elasticity of Human Bioartificial Tendons

Stiffness is an important mechanical property of connective tissues, especially for tissues subjected to cyclic strain in vivo, such as tendons. Therefore, modulation of material properties of native or engineered tissues is an important consideration for tissue repair. Interleukin 1-beta (IL-1beta) is a cytokine most often associated in connective tissues with induction of matrix metalloproteinases and matrix destruction. However, IL-1beta may also be involved in constructive remodeling and confer a cell survival value to tenocytes. In this study, we investigated the effects of IL-1beta on the properties of human tenocyte-populated bioartificial tendons (BATs) fabricated in a novel three-dimensional (3D) culture system. IL-1beta treatment reduced the ultimate tensile strength and elastic modulus of BATs and increased the maximum strain. IL-1beta at low doses (1, 10 pM) upregulated elastin expression and at a high dose (100 pM) downregulated type I collagen expression. Matrix metalloproteinases, which are involved in matrix remodeling, were also upregulated by IL-1beta. The increased elasticity prevented BATs from rupture caused by applied strain. The results in this study suggest that IL-1beta may act as a defense/survival factor in response to applied mechanical loading. The balance between cell intrinsic strain and external matrix strain is important for maintaining the integrity of tendons.

Interplay of Sps and poly(C) binding protein 1 on the mu-opioid receptor gene expression

The proximal promoter of mouse mu-opioid receptor (MOR) gene is the dominant promoter for directing MOR-1 gene expression in brain. Sp1/Sp3 (Sps) and poly(C) binding protein 1 (PCBP) bind to a cis-element of MOR proximal promoter. Functional interaction between Sps and PCBP and their individual roles on MOR proximal core promoter were investigated using SL2 cells, devoid of Sps and PCBP. Each factor contributed differentially to the promoter, with a rank order of activity Sp1>Sp3>PCBP. Functional analysis suggested the interplay of Sps and PCBP in an additive manner. The in vivo binding of individual Sps or PCBP to MOR proximal promoter was demonstrated using chromatin immunoprecipitation (ChIP). Re-ChIP assays further suggested simultaneous bindings of Sps and PCBP to the proximal promoter, indicating physiologically relevant communication between Sps and PCBP. Collectively, results documented that a functional coordination between Sps and PCBP contributed to cell-specific MOR gene expression.

Insulin-like growth factor I promoter polymorphism, risk of stroke, and survival after stroke: the Rotterdam study

BACKGROUND AND PURPOSE

Low levels of insulin-like growth factor I (IGF-I) predispose to atherosclerosis and may therefore increase the risk of stroke. Low levels have also been found to influence the outcome of cardiovascular and cerebrovascular disease. A polymorphism in the promoter region of the IGF-I gene influences IGF-I levels. Non-carriers of the 192 bp allele have lower levels of IGF-I compared with 192 bp allele carriers. We studied the IGF-I polymorphism in relation to the risk of stroke and survival after stroke.

METHODS

We studied 6808 subjects of the Rotterdam Study, who were followed for the occurrence of stroke and death after stroke. Subjects were grouped according to the 192 bp allele of IGF-I into non-carriers, heterozygotes, and homozygotes. The risk of stroke and survival after stroke was studied using Cox regression analysis, adjusting for age and sex, with homozygotes for the wildtype allele as the reference.

RESULTS

Non-carriers had a relative risk of 0.8 (95% CI: 0.6 to 1.0) for the occurrence of any stroke and 0.7 (95% CI: 0.5 to 1.0) for ischaemic stroke. For non-carriers, the relative risk of death after any stroke was 1.5 (95% CI: 1.0 to 2.2). After an ischaemic stroke, this relative risk was 1.5 (95% CI: 0.9 to 2.6) and after a haemorrhagic stroke 5.2 (95% CI: 1.3 to 21.5).

CONCLUSIONS

Our study suggests that IGF-I is a significant determinant of survival after stroke.

Insulin-like growth factors and coronary heart disease

Insulin-like growth factor-1 (IGF-I), the primary mediator of growth hormone (GH) effects, is an important regulator of cell growth, differentiation, and apoptosis. GH and IGF-I deficiency is known to be associated with premature atherosclerosis and elevated cardiovascular disease mortality. Recent evidence suggests that cardiovascular disease risk may also be elevated among apparently healthy individuals who have serum IGF-I levels in the low-normal range. In this review, we appraise the epidemiologic and clinical studies implicating low IGF-I level as a risk factor for incident myocardial infarction and other manifestations of coronary heart disease. Potential mechanisms that may underlie this association include beneficial effects of IGF-I on myocyte survival after ischemia, stability of atherosclerotic lesions, and endothelial function. We conclude that additional confirmatory data from prospective studies are needed to confirm low IGF-I level as an independent cardiovascular risk factor. However, if this finding is confirmed, this would support the rationale for intervention trials aimed at reducing cardiovascular disease morbidity and mortality among older adults by targeting the GH/IGF-I pathway.

Sp1 and Sp3 regulate basal transcription of the human CYP2F1 gene

Selective transcription of the human CYP2F1 gene in lung tissues may control the susceptibilities of this organ to diverse pneumotoxicants and lung carcinogens. However, the mechanisms responsible for CYP2F1 organ-selective transcription have not been elucidated. The objectives of the current studies were to identify and characterize basal transcription elements within the TATA-less promoter region of CYP2F1. Four putative Sp1-like sites were identified in the CYP2F1 promoter. Competitive electrophoretic mobility shift assay analysis with mutated oligonucleotide probes and lung A549 cell nuclear extract, along with supershift studies using antibodies to either Sp1 or Sp3 proteins, demonstrated that all four sites formed three specific protein-DNA complexes. Mutations in any of the four core Sp1-like motifs abolished protein-DNA binding. Western blot analysis of both human tissues and cells showed that Sp1 was considerably higher in lung than liver and that Sp3 was much higher in liver than lung. Promoter activation of a luciferase reporter construct was sequentially increased by addition of each of the four Sp1-like motifs in lung A549 cells but not in liver HepG2 cells. Cotransfection of a Sp1 expression vector with the reporter construct dramatically increased luciferase activity in either A549 cells or Sp1-deficient Drosophila Schneider line 2 (SL-2) cells. However, similar cotransfections with an Sp3 expression vector failed to increase activity. Cotransfection of both the Sp1 and Sp3 expression vectors considerably decreased Sp1-mediated activity in A549 cells and abolished activity in SL-2 cells. Thus, these studies demonstrated that four Sp1-dependent proximal promoter elements drive organ-selective CYP2F1 gene transcription, and that Sp1 and Sp3 factors interact to modulate constitutive CYP2F1 transcription in lung cells.

Sumoylation of internally initiated Sp3 isoforms regulates transcriptional repression via a Trichostatin A-insensitive mechanism

Sp3 is a ubiquitously expressed member of the Sp family of transcription factors that encodes three proteins, Sp3, M1 and M2, with differing capacities to stimulate or repress transcription. As part of ongoing efforts to study the functions of Sp3 isoforms, we employed a yeast "two-hybrid" screen to identify Sp3-binding proteins. This screen resulted in the identification of Ubc9, a SUMO-1 conjugating enzyme, as an M2-binding protein, and consistent with these results sequence analyses identified consensus sumoylation motifs within several Sp family members. Western blots probed with anti-Sp3 detected a high molecular weight Sp3 isoform that is stabilized by a SUMO-1 hydrolase inhibitor, and this protein is also bound by anti-SUMO-1 antiserum. Transient transfection assays with epitope-tagged-SUMO-1 and GFP-SUMO-1 fusion proteins confirmed that Sp3, M1 and M2 proteins are sumoylated in vivo. Substitution of arginine for lysine at one putative site of sumoylation, lysine(551), blocked sumoylation of all Sp3 isoforms in vivo and led to a marginal increase in Sp3-mediated trans-activation in insect and mammalian cells. In contrast, introduction of this amino acid substitution within M1 converted it into a potent transcriptional trans-activator. We conclude that Sp3 isoforms are sumoylated in vivo and this post-translational modification plays an important role in the regulation of Sp3-mediated transcription.

Elastin

Elastin is a key extracellular matrix protein that is critical to the elasticity and resilience of many vertebrate tissues including large arteries, lung, ligament, tendon, skin, and elastic cartilage. Tropoelastin associates with multiple tropoelastin molecules during the major phase of elastogenesis through coacervation, where this process is directed by the precise patterning of mostly alternating hydrophobic and hydrophilic sequences that dictate intermolecular alignment. Massively crosslinked arrays of tropoelastin (typically in association with microfibrils) contribute to tissue structural integrity and biomechanics through persistent flexibility, allowing for repeated stretch and relaxation cycles that critically depend on hydrated environments. Elastin sequences interact with multiple proteins found in or colocalized with microfibrils, and bind to elastogenic cell surface receptors. Knowledge of the major stages in elastin assembly has facilitated the construction of in vitro models of elastogenesis, leading to the identification of precise molecular regions that are critical to elastin-based protein interactions.

von Hippel-Lindau partner Jade-1 is a transcriptional co-activator associated with histone acetyltransferase activity

Jade-1 was identified as a protein partner of the von Hippel-Lindau tumor suppressor pVHL. The interaction of Jade-1 and pVHL correlates with renal cancer risk. We have investigated the molecular function of Jade-1. Jade-1 has two zinc finger motifs called plant homeodomains (PHD). A line of evidence suggests that the PHD finger functions in chromatin remodeling and protein-protein interactions. We determined the cellular localization of Jade-1 and examined whether Jade-1 might have transcriptional and histone acetyltransferase (HAT) functions. Biochemical cell fractionation studies as well as confocal images of cells immunostained with a specific Jade-1 antibody revealed that endogenous Jade-1 is localized predominantly in the cell nucleus. Tethering of Gal4-Jade-1 fusion protein to Gal4-responsive promoters in co-transfection experiments activated transcription 5-6-fold, indicating that Jade-1 is a possible transcriptional activator. It was remarkable that overexpression of Jade-1 in cultured cells specifically increased levels of endogenous acetylated histone H4, but not histone H3, strongly suggesting that Jade-1 associates with HAT activity specific for histone H4. Deletion of the two PHD fingers completely abolished Jade-1 transcriptional and HAT activities, indicating that these domains are indispensable for Jade-1 nuclear functions. In addition, we demonstrated that TIP60, a known HAT with histone H4/H2A specificity, physically associates with Jade-1 and is able to augment Jade-1 HAT function in live cells, strongly suggesting that TIP60 might mediate Jade-1 HAT activity. Thus, Jade-1 is a novel candidate transcriptional co-activator associated with HAT activity and may play a key role in the pathogenesis of renal cancer and von Hippel-Lindau disease.

Heparin-binding EGF-like growth factor regulates elastin and FGF-2 expression in pulmonary fibroblasts

Elastase degradation of elastin within alveolar walls is an important event in the development of pulmonary emphysema. In addition to elastolytic activities, elastases release growth factors from extracellular matrices and interstitial cell surfaces that can regulate elastogenesis and other cellular responses. In the present study, we demonstrate that brief treatment of matrix-laden rat pulmonary fibroblast cultures with pancreatic elastase results in the release of soluble heparin-binding epidermal growth factor-like growth factor (HB-EGF) concomitant with a decrease in HB-EGF binding to both heparan sulfate proteoglycan and receptor sites on the cells. In undigested, matrix-laden fibroblasts, HB-EGF significantly downregulates elastin mRNA via activation of epidermal growth factor receptor. Results from nuclear run-on analyses show that HB-EGF downregulates elastin mRNA via transcriptional suppression. HBEGF treatment stimulates MAP or ERK kinase (MEK)-dependent ERK1/2 phosphorylation and leads to nuclear accumulation of Fra-1. Blocking ERK1/2 activation by MEK1/2 inhibitors (PD-98059 or U-0126) diminishes HB-EGF-induced Fra-1 accumulation and subsequent downregulation of elastin mRNA. Coaddition of two elastase-released growth factors, HB-EGF and FGF-2, results in an additive inhibitory effect on elastin mRNA levels. Furthermore, HB-EGF addition to pulmonary fibroblasts increases FGF-2 mRNA and protein levels. These data suggest that HB-EGF and FGF-2 act in concert to regulate the synthesis of elastin in injury/repair situations.

IGF-I activity may be a key determinant of stroke risk--a cautionary lesson for vegans

IGF-I acts on vascular endothelium to activate nitric oxide synthase, thereby promoting vascular health; there is reason to believe that this protection is especially crucial to the cerebral vasculature, helping to ward off thrombotic strokes. IGF-I may also promote the structural integrity of cerebral arteries, thereby offering protection from hemorrhagic stroke. These considerations may help to explain why tallness is associated with low stroke risk, whereas growth hormone deficiency increases stroke risk--and why age-adjusted stroke mortality has been exceptionally high in rural Asians eating quasi-vegan diets, but has been declining steadily in Asia as diets have become progressively higher in animal products. There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat--both characteristic of those adopting low-fat vegan diets--may also increase stroke risk. Vegans are thus well advised to adopt practical countermeasures to minimize stroke risk--the most definitive of which may be salt restriction. A high potassium intake, aerobic exercise training, whole grains, moderate alcohol consumption, low-dose aspirin, statin or policosanol therapy, green tea, and supplementation with fish oil, taurine, arginine, and B vitamins--as well as pharmacotherapy of hypertension if warranted--are other practical measures for lowering stroke risk. Although low-fat vegan diets may markedly reduce risk for coronary disease, diabetes, and many common types of cancer, an increased risk for stroke may represent an 'Achilles heel'. Nonetheless, vegans have the potential to achieve a truly exceptional 'healthspan' if they face this problem forthrightly by restricting salt intake and taking other practical measures that promote cerebrovascular health.

Transcriptional regulation of pulmonary elastin gene expression in elastase-induced injury

Previously we have shown that treatment of confluent, pulmonary fibroblast cultures with elastase results in upregulation of elastin mRNA and protein levels. In the present study we focused on determining the level at which elastin expression is upregulated after elastase exposure. We examined as models for this investigation elastin gene expression in primary pulmonary fibroblast cells during the transition from subconfluent to confluent cultures and in confluent, matrix-laden cultures treated briefly with elastase. In addition, we extended our studies to mice that were given an intratracheal dose of elastase; the effects on lung elastin mRNA and elastin promoter activity levels were measured and compared with results from in vitro cell models. The results demonstrate that upregulation of elastin gene expression during the transition of subconfluent to confluent cultures and after elastase injury is associated with an increase in the level of transcription both in vitro and in vivo. Furthermore, intratracheal administration of elastase to transgenic mice illustrates that the increased levels of elastin mRNA are accompanied by increased activity of the elastin gene promoter in cells spatially positioned near major sites of tissue injury.

A low-fat, whole-food vegan diet, as well as other strategies that down-regulate IGF-I activity, may slow the human aging process

A considerable amount of evidence is consistent with the proposition that systemic IGF-I activity acts as pacesetter in the aging process. A reduction in IGF-I activity is the common characteristic of rodents whose maximal lifespan has been increased by a wide range of genetic or dietary measures, including caloric restriction. The lifespans of breeds of dogs and strains of rats tend to be inversely proportional to their mature weight and IGF-I levels. The link between IGF-I and aging appears to be evolutionarily conserved; in worms and flies, lifespan is increased by reduction-of-function mutations in signaling intermediates homologous to those which mediate insulin/IGF-I activity in mammals. The fact that an increase in IGF-I activity plays a key role in the induction of sexual maturity, is consistent with a broader role for-IGF-I in aging regulation. If down-regulation of IGF-I activity could indeed slow aging in humans, a range of practical measures for achieving this may be at hand. These include a low-fat, whole-food, vegan diet, exercise training, soluble fiber, insulin sensitizers, appetite suppressants, and agents such as flax lignans, oral estrogen, or tamoxifen that decrease hepatic synthesis of IGF-I. Many of these measures would also be expected to decrease risk for common age-related diseases. Regimens combining several of these approaches might have a sufficient impact on IGF-I activity to achieve a useful retardation of the aging process. However, in light of the fact that IGF-I promotes endothelial production of nitric oxide and may be of especial importance to cerebrovascular health, additional measures for stroke prevention-most notably salt restriction-may be advisable when attempting to down-regulate IGF-I activity as a pro-longevity strategy.

Sp1 and Sp3 recruit histone deacetylase to repress transcription of human telomerase reverse transcriptase (hTERT) promoter in normal human somatic cells

Activation of telomerase is crucial for cells to gain immortality. In human cells, telomerase activity is tightly regulated by the expression of its catalytic subunit, human telomerase reverse transcriptase (hTERT). In most normal human somatic cells, hTERT is not expressed, and its suppression acts as an important gatekeeper against tumorigenesis. Here we describe the systematic analyses of hTERT promoter to understand the transcriptional repression mechanism of the hTERT gene in normal human somatic cells. Through the serial deletion analysis of hTERT promoter in normal human fibroblasts, we identified a critical repressive element on the hTERT promoter. The repressive element formed DNA-protein complexes with Sp1 and Sp3 in nuclear extracts. Using formaldehyde cross-linked chromatin immunoprecipitation analysis, we found that Sp1 and Sp3 were associated with the endogenously repressed hTERT promoter in human fibroblasts. Furthermore, Sp1 and Sp3 interacted with histone deacetylase (HDAC) in these cells. Overexpression of dominant-negative mutants of Sp1 and Sp3, which contained mainly the HDAC2-binding domain, relieved the HDAC-mediated repression of the hTERT promoter. Taken together, these results suggest that Sp1 and Sp3 associate with the hTERT promoter, recruiting HDAC for the localized deacetylation of nucleosomal histones and transcriptional silencing of the hTERT gene in normal human somatic cells.

Aspiration cytology of elastofibroma dorsi: case report with ultrastructural and immunohistochemical findings

Elastofibroma is a well-recognized tumor-like process which typically occurs in the soft tissue of the shoulder. Although fine-needle aspiration (FNA) represents a quick and simple method for definitive diagnosis, the possibility of a false-negative diagnosis is high due to the hypocellularity of the smears. However, a high index of suspicion based on the clinical presentation of a firm mass in a typical location in an elderly person, usually female, aids in the diagnosis. We describe the FNA findings of elastofibroma dorsi in an 89-yr-old woman which, although hypocellular, contained diagnostic aggregates of petaloid globules within a collagenous matrix. The cytologic material showed a green-yellow autofluorescence of the altered elastic fibers with ultraviolet light. Transmission electron microscopy revealed an elongated beaded appearance with small electron densities and obliteration of the central elastin core. The presence of a hypocellular aspirate with autofluorescent elastic fibers should suggest the possibility of elastofibroma dorsi.

Characterization of the mouse aortic carboxypeptidase-like protein promoter reveals activity in differentiated and dedifferentiated vascular smooth muscle cells

The dedifferentiation and proliferation of vascular smooth muscle cells (VSMCs) contribute to the formation of vascular lesions. In this study, the regulation of aortic carboxypeptidase-like protein (ACLP) expression in VSMCs was investigated. After mouse carotid injury, the expression of ACLP increases in the dedifferentiated VSMCs of the neointima in a pattern that differs from that of smooth muscle alpha-actin. To better understand the regulation of ACLP in VSMCs, we characterized the 21-exon mouse ACLP gene and 5'-flanking region and examined its promoter activity. In transient transfection assays, 2.5 kb of the ACLP 5'-flanking sequence directed high levels of luciferase reporter activity in primary cultured rat aortic smooth muscle cells, and this activity was not dependent on serum response factor. We identified a positive element between base pairs -156 and -122 by analysis of 5' deletion and mutant constructs. By use of electrophoretic mobility shift assays with rat aortic smooth muscle cell nuclear extracts, Sp1 and Sp3 transcription factors bound to this region, and transfection assays in D.Mel.2 cells revealed that both Sp1 and Sp3 transactivated the ACLP promoter. Transgenic mice harboring the -2.5-kb ACLP promoter upstream from a nuclear-targeted LacZ gene were generated, and expression was detected in the VSMCs of large blood vessels, arterioles, and veins. Interestingly, ACLP promoter-LacZ reporter activity increased within the neointimal VSMCs of injured carotid vessels, consistent with the expression of the endogenous ACLP protein. The ACLP promoter may provide a novel tool to target gene expression to dedifferentiated VSMCs.

Cloning and characterization of the human heparanase-1 (HPR1) gene promoter: role of GA-binding protein and Sp1 in regulating HPR1 basal promoter activity

Heparanase-1 (HPR1) is an endoglycosidase that specifically degrades the heparan sulfate chains of proteoglycan, a component of blood vessel walls and the extracellular matrix. Recent studies demonstrated that HPR1 expression is increased in a variety of malignancies and may play a critical role in tumor metastases. The HPR1 gene and its genomic structure have been recently cloned and characterized. To understand the mechanisms of HPR1 gene expression and regulation, we first mapped the transcription start site of the HPR1 gene and found that HPR1 mRNA was transcribed from the nucleotide position 101 bp upstream of the ATG codon. A 3.5-kb promoter region of the HPR1 gene was cloned. Sequence analysis revealed that the TATA-less, GC-rich promoter of the HPR1 gene belongs to the family of housekeeping genes. This 3.5-kb promoter region exhibited strong promoter activity in two thyroid tumor cell lines. Truncation analysis of the HPR1 promoter identified a minimal 0.3-kb region that had strong basal promoter activity. Truncation and mutational analysis of the HPR1 promoter revealed three Sp1 sites and four Ets-relevant elements (ERE) significantly contributing to basal HPR1 promoter activity. Binding to the Sp1 sites by Sp1 and to the ERE sites by GA-binding protein (GABP) was confirmed by electrophoretic mobility shift assay and competition and supershift electrophoretic mobility shift assays. Cotransfection of Sp- and GABP-deficient Drosophila SL-2 cells with the HPR1 promoter-driven luciferase construct plus the expression vector encoding the Sp1, Sp3, or GABP gene induced luciferase gene expression. Mutation or truncation of the Sp1 or ERE sites reduced luciferase expression in both SL-2 cells and thyroid tumor cell lines. Coexpression of GABPalpha/beta and Sp1 or Sp3 further increased luciferase reporter gene expression. Our results collectively suggest that Sp1 cooperates with GABP to regulate HPR1 promoter activity.

Functional components of basic fibroblast growth factor signaling that inhibit lung elastin gene expression

Previously, we have demonstrated that basic fibroblast growth factor (bFGF) decreases elastin gene transcription in confluent rat lung fibroblasts via the binding of a Fra-1-c-Jun heterodimer to an activator protein-1-cAMP response element in the distal region of the elastin promoter. In the present study, we show that bFGF activates the mitogen-activated protein kinase extracellular signal-regulated kinase 1/2, resulting in the translocation of phosphorylated extracellular signal-regulated kinase 1/2 into the nucleus followed by increased binding of Elk-1 to the serum response element of the c-Fos promoter, transient induction of c-Fos mRNA, and sustained induction of Fra-1 mRNA. The addition of PD-98059, an inhibitor of mitogen-activated protein kinase kinase, abrogates the bFGF-dependent repression of elastin mRNA expression. Comparative analyses of confluent and subconfluent fibroblast cultures reveal significant differences in elastin mRNA levels and activator protein-1 protein factors involved in the regulation of elastin transcription. These findings suggest that bFGF modulates specific cellular events that are dependent on the state of the cell and provide a rationale for the differential responses that can be expected in development and injury or repair situations.

Sp1 and krüppel-like factor family of transcription factors in cell growth regulation and cancer

The Sp/KLF family contains at least twenty identified members which include Sp1-4 and numerous krüppel-like factors. Members of the family bind with varying affinities to sequences designated as 'Sp1 sites' (e.g., GC-boxes, CACCC-boxes, and basic transcription elements). Family members have different transcriptional properties and can modulate each other's activity by a variety of mechanisms. Since cells can express multiple family members, Sp/KLF factors are likely to make up a transcriptional network through which gene expression can be fine-tuned. 'Sp1 site'-dependent transcription can be growth-regulated, and the activity, expression, and/or post-translational modification of multiple family members is altered with cell growth. Furthermore, Sp/KLF factors are involved in many growth-related signal transduction pathways and their overexpression can have positive or negative effects on proliferation. In addition to growth control, Sp/KLF factors have been implicated in apoptosis and angiogenesis; thus, the family is involved in several aspects of tumorigenesis. Consistent with a role in cancer, Sp/KLF factors interact with oncogenes and tumor suppressors, they can be oncogenic themselves, and altered expression of family members has been detected in tumors. Effects of changes in Sp/KLF factors are context-dependent and can appear contradictory. Since these factors act within a network, this diversity of effects may arise from differences in the expression profile of family members in various cells. Thus, it is likely that the properties of the overall network of Sp/KLF factors play a determining role in regulation of cell growth and tumor progression.

A pancreatic beta -cell-specific enhancer in the human PDX-1 gene is regulated by hepatocyte nuclear factor 3beta (HNF-3beta ), HNF-1alpha, and SPs transcription factors

The PDX-1 transcription factor plays a key role in pancreas development. Although expressed in all cells at the early stages, in the adult it is mainly restricted to the beta-cell. To characterize the regulatory elements and potential transcription factors necessary for human PDX-1 gene expression in beta-cells, we constructed a series of 5' and 3' deletion fragments of the 5'-flanking region of the gene, fused to the luciferase reporter gene. In this report, we identify by transient transfections in beta- and non-beta-cells a novel beta-cell-specific distal enhancer element located between -3.7 and -3.45 kilobases. DNase I footprinting analysis revealed two protected regions, one binding the transcription factors SP1 and SP3 and the other hepatocyte nuclear factor 3beta (HNF-3beta) and HNF-1alpha. Cotransfection experiments suggest that HNF-3beta, HNF-1alpha, and SP1 are positive regulators of the herein-described human PDX-1 enhancer element. Furthermore, mutations within each motif abolished the binding of the corresponding factor(s) and dramatically impaired the enhancer activity, therefore suggesting cooperativity between these factors.

Elastofibroma dorsi: elaboration of cytologic features and review of its pathogenesis

Elastofibroma is a slow-growing soft tissue lesion characteristically found between the inferior scapula and chest wall. Because it behaves clinically in a benign manner, fine-needle aspiration (FNA) represents the simplest and quickest method of obtaining a definitive diagnosis, thus obviating more invasive means of obtaining a tissue diagnosis. However, due to the nature of this lesion a correct diagnosis can inadvertently be missed. Herein we describe the findings of a recent FNA that obtained abundant diagnostic material and elaborate upon the spectrum of cytologic features of the elastic fibers that can be identified. These features should be recognized, since aspiration biopsy in elastofibromas can lead to hypocellular smears. In addition, we discuss recent developments in the pathophysiology of elastic fibers and their application toward understanding the generation of an elastofibroma.

Activation of telomerase rna gene promoter activity by NF-Y, Sp1, and the retinoblastoma protein and repression by Sp3

Expression of the human telomerase RNA component gene, hTERC is essential for telomerase activity. The hTERC gene is expressed during embryogenesis and then downregulated during normal development, leaving most adult somatic cells devoid of hTERC expression. During oncogenesis, however, hTERC is re-expressed consequently contributing to the unrestricted proliferative capacity of many human cancers. Thus the identification of the molecular basis for the regulation of the telomerase RNA component gene in normal cells and its deregulation in cancer cells is of immediate interest. We have previously cloned the hTERC promoter and in this study have identified several transcription factors that modulate the expression of hTERC. We demonstrate that NF-Y binding to the CCAAT region of the hTERC promoter is essential for promoter activity. Sp1 and the retinoblastoma protein (pRb) are activators of the hTERC promoter and Sp3 is a potent repressor. These factors appear to act in a species-specific manner. Whereas Sp1 and Sp3 act on the human, bovine, and mouse TERC promoters, pRb activates only the human and bovine promoter, and NF-Y is only essential for the human TERC gene.

Involvement of Sp1 in the transcriptional regulation of the rat insulin-like growth factor-1 gene

Most insulin-like growth factor-I (IGF-I) transcripts are initiated in exon 1, but mechanisms of regulation are not well understood. Since potential Sp1 sites are found in footprinted regions within approximately 360 bp upstream and downstream from the major initiation sites in exon 1, we explored the involvement of Sp1 and Sp3 in regulation of IGF-1 expression. Gel shift assays showed strong Sp1 binding to the downstream site, but binding to the upstream site was weak; Sp1 bound to a CCTGCCCA sequence in downstream footprint region V, and Sp3 binding was centered on the same sequence. IGF-I basal promoter constructs containing a mutation in the downstream Sp1 site exhibited a 32% decrease in expression in CHO cells and a 75% decrease in HepG2 cells, indicating the importance of Sp1 for expression in vivo. Sp1 and Sp3 expression vectors provided three- to five-fold stimulation of wild-type IGF-I constructs, but had little effect on a construct containing a mutation in the downstream Sp1 site, and Sp1 had comparable effects in Drosophila SL2 cells. IGF-I heterologous promoter constructs exhibited similar responses: in both SL2 cells and CHO cells, stimulation by Sp1 was enhanced with constructs containing downstream region V. Since Sp1 also stimulated expression of concatamers of putative cis-acting sites fused to the SV40 promoter enhancer in pGL3, the results in combination indicate that the presence of IGF-I region V is sufficient to permit stimulation by Sp1.

CONCLUSION

Sp1 and related factors may play an important role in the regulation of IGF-I gene transcription, through interactions with region V downstream from the major initiation sites in exon 1.