The Effects of Heat Exposure on Vaginal Smooth Muscle Cells: Elastin and Collagen Production.

AIMS: To evaluate smooth muscle cells (SMCs) proliferation and elastin and collagen production after heat exposure (65°C). METHODS: Samples were taken from the anterior vaginal wall, SMCs were cultured, and heated to 65°C for 30 and 60 s. Cell proliferation was assessed; tropoelastin and collagen production was measured. RESULTS: Heat does not affect SMC proliferation at 65°C neither at 30 nor at 60 s. Surface-deposited elastin level was significantly increased after heat exposure (mean ± SD, 30 s 155 ± 5% of control [p < 0.01] and 60 s 516 ± 40% of control [p < 0.01]). Tropoelastin levels in the culture media were significantly lower after 60 s of heat exposure (mean ± SD, 30 s 102 ± 5% of control [p = ns] and 60 s 70 ± 2% of control [p = 0.04]). Significant increase in surface-deposited collagen production was found (mean ± SD, 30 s 170 ± 6% of control [p < 0.01] and 60 s 123 ± 6% of control [p < 0.01]), but no such elevation was measured in the media after heat exposure (mean ± SD, 30 s 120 ± 20% of control [p = ns] and 60 s 100 ± 20% of control [p = ns]). CONCLUSION: When SMCs are exposed to heat there is significant elevation in collagen and elastin production. Changes in the composition of the extracellular matrix after heat exposure may contribute to vaginal wall remodeling.

Lactoferrin induces tropoelastin expression by activating the lipoprotein receptor-related protein 1-mediated phosphatidylinositol 3-kinase/Akt pathway in human dermal fibroblasts.

Dermal fibroblasts generate the extracellular matrix component elastin, which is synthesized as tropoelastin (TE) and play a critical role in maintaining skin elasticity. Lactoferrin (Lf), an 80-kDa iron-binding glycoprotein, has biological functions such as anti-bacterial, -inflammatory, and -cancer activities. We previously reported that bovine Lf increases TE mRNA expression in human dermal fibroblasts. However, it remains unclear how Lf up-regulates TE expression. Here, we investigated molecular mechanisms underlying this effect. Lf promoted the phosphorylation of Akt1 and extracellular signal-regulated protein kinase (ERK)1/2. As expected, the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 and the MAPK inhibitor U0126 inhibited Lf-induced phosphorylation of Akt1 and ERK1/2, respectively. In contrast, LY294002, but not U0126, inhibited Lf-induced TE expression. Human dermal fibroblasts expressed lipoprotein receptor-related protein 1 (LRP-1) mRNA, and the LRP1 inhibitor receptor-associated protein attenuated Lf-induced increases in TE expression. Furthermore, siRNA-mediated knockdown of LRP-1 significantly suppressed Lf-increased TE expression and Lf-induced Akt1 phosphorylation. Iron-saturated Lf (holo-Lf) increased TE expression and promoted Akt1 phosphorylation, when compared to those parameters in cells treated with iron-free Lf (apo-Lf). Transforming growth factor (TGF)-ß1 also increased TE expression. LY294002 inhibited TGF-ß1-mediated TE upregulation, whereas TGF-ß1 activated Akt2, but not Akt1, phosphorylation. These results indicate that holo-Lf, but not apo-Lf, increases TE expression through LRP-1 in human dermal fibroblasts and suggest that holo-Lf and TGF-ß1 enhance TE expression by activating the PI3K/Akt1 and PI3K/Akt2 pathways, respectively.

Inhibition of versican expression by siRNA facilitates tropoelastin synthesis and elastic fiber formation by human SK-LMS-1 leiomyosarcoma smooth muscle cells in vitro and in vivo.

Versican is an extracellular matrix (ECM) molecule that interacts with other ECM components to influence ECM organization, stability, composition, and cell behavior. Versican is known to increase in a number of cancers, but little is known about how versican influences the amount and organization of the ECM components in the tumor microenvironment. In the present study, we modulated versican expression using siRNAs in the human leiomyosarcoma (LMS) smooth muscle cell line SK-LMS-1, and observed the formation of elastin and elastic fibers in vitro and also in vivo in a nude mouse tumor model. Constitutive siRNA-directed knockdown of versican in LMS cells resulted in increased levels of elastin, as shown by immunohistochemical staining of the cells in vitro, and by mRNA and protein analyses. Moreover, versican siRNA LMS cells, when injected into nude mice, generated smaller tumors that had significantly greater immunohistochemical and histochemical staining for elastin when compared to control tumors. Additionally, microarray analyses were used to determine the influence of versican isoform modulation on gene expression profiles, and to identify genes that influence and relate to the process of elastogenesis. cDNA microarray analysis and TaqMan low density array validation identified previously unreported genes associated with downregulation of versican and increased elastogenesis. These results highlight an important role for the proteoglycan versican in regulating the expression and assembly of elastin and the phenotype of LMS cells.

Expression of synthetic human tropoelastin (hTE) protein in Nicotiana tabacum.

Plant molecular farming (PMF) is an important growing prospective approach in plant biotechnology; it includes production of recombinant pharmaceutical and industrial proteins in large quantities from engineered plants. Elastin is a major protein component of tissues that require elasticity, it helps keep skin smooth as it stretches to allow normal. Elastin is used as a raw material for the cosmetic industry. In this work, we aimed to use plant as a bioreactor for the expression and production of the full human tropoelastin protein. Agrobacterium- mediated transient expression system into Nicotiana tabacum using syringe agroinfiltration was used to provide fast and convenient way to produce recombinant proteins with greater expression overall the plant leaf. This study aimed to establish an efficient and rapid system for transiently expression and production of human recombinant tropoelastin protein in transgenic N. tabacum plants. Modified elastin (ELN) gene was biosynthesized and cloned into pCambia1390 vector to be used into N. tabacum agroinfilteration. Optimization of codon usage for the human tropoelastin gene, without changing the primary structure of the protein was carried out to ensure high expression in tobacco plants. The obtained data proved that the 5(th) day post-infiltration is the optimum interval to obtain the maximum production of our recombinant protein. Southern blot analysis was able to detect 2175 bp fragment length representing the ELN orf (open reding frame). On the other hand, ELN -expression within plant's tissue was visualized by RT-PCR during the period 3-10 days post agroinfiltration. At the protein level, western and ELISA confirmed the expression of recombinant tropoelastin protein. Western blot analysis detected the tropoelastin protein as parent band at ∼70 kDa from freshly extracted protein, while two degraded bands of ∼55 and ∼45 kDa, representing a pattern of tropoelastin were appeared with frozen samples. This study showed that biosynthetic ELN gene was successfully expressed into N. tabacum leaves using agroinfiltration technique.

Elastogenesis at the onset of human cardiac valve development.

Semilunar valve leaflets have a well-described trilaminar histoarchitecture, with a sophisticated elastic fiber network. It was previously proposed that elastin-containing fibers play a subordinate role in early human cardiac valve development; however, this assumption was based on data obtained from mouse models and human second and third trimester tissues. Here, we systematically analyzed tissues from human fetal first (4-12 weeks) and second (13-18 weeks) trimester, adolescent (14-19 years) and adult (50-55 years) hearts to monitor the temporal and spatial distribution of elastic fibers, focusing on semilunar valves. Global expression analyses revealed that the transcription of genes essential for elastic fiber formation starts early within the first trimester. These data were confirmed by quantitative PCR and immunohistochemistry employing antibodies that recognize fibronectin, fibrillin 1, 2 and 3, EMILIN1 and fibulin 4 and 5, which were all expressed at the onset of cardiac cushion formation (~week 4 of development). Tropoelastin/elastin protein expression was first detectable in leaflets of 7-week hearts. We revealed that immature elastic fibers are organized in early human cardiovascular development and that mature elastin-containing fibers first evolve in semilunar valves when blood pressure and heartbeat accelerate. Our findings provide a conceptual framework with the potential to offer novel insights into human cardiac valve development and disease.

Fractional versus ablative erbium:yttrium-aluminum-garnet laser resurfacing for facial rejuvenation: an objective evaluation.

BACKGROUND: Laser is one of the main tools for skin resurfacing. Erbium:yttrium-aluminum-garnet (Er:YAG) was the second ablative laser, after carbon dioxide, emitting wavelength of 2940 nm. Fractional laser resurfacing has been developed to overcome the drawbacks of ablative lasers. OBJECTIVE: We aimed to objectively evaluate the histopathological and immunohistochemical effects of Er:YAG 2940-nm laser for facial rejuvenation (multiple sessions of fractional vs single session of ablative Er:YAG laser). METHODS: Facial resurfacing with single-session ablative Er:YAG laser was performed on 6 volunteers. Another 6 were resurfaced using fractional Er:YAG laser (4 sessions). Histopathological (hematoxylin-eosin, orcein, Masson trichrome, and picrosirius red stains) and immunohistochemical assessment for skin biopsy specimens were done before laser resurfacing and after 1 and 6 months. Histometry for epidermal thickness and quantitative assessment for neocollagen formation; collagen I, III, and VII; elastin; and tropoelastin were done for all skin biopsy specimens. RESULTS: Both lasers resulted in increased epidermal thickness. Dermal collagen showed increased neocollagen formation with increased concentration of collagen types I, III, and VII. Dermal elastic tissue studies revealed decreased elastin whereas tropoelastin concentration increased after laser resurfacing. Neither laser showed significant difference between their effects clinically and on dermal collagen. Changes in epidermal thickness, elastin, and tropoelastin were significantly more marked after ablative laser. LIMITATIONS: The small number of patients is a limitation, yet the results show significant improvement. CONCLUSION: Multiple sessions of fractional laser have comparable effects to a single session of ablative Er:YAG laser on dermal collagen but ablative laser has more effect on elastic tissue and epidermis.

Signaling molecules in the fetal rabbit model for congenital diaphragmatic hernia.

RATIONALE AND OBJECTIVES: Little is known about molecular changes in lungs of fetal rabbits with surgically induced diaphragmatic hernia (DH). Therefore, we examined in this model gene expressions of pivotal molecules for the developing lung. METHODS: At day 23 of gestation, DH was created in 12 fetuses from 4 does. Both lungs from six live DH fetuses and from six unoperated controls were harvested and weighed at term. Transcription of 15 genes involved in alveolarization, angiogenesis, regulation of vascular tone, or epithelial maturation was investigated by real-time quantitative polymerase chain reaction. MAIN RESULTS: DH decreased lung-to-body weight ratio (P < 0.001). A bilateral downregulation was seen for genes encoding for tropoelastin (P < 0.01), lysyl oxidase (P < 0.05), fibulin 5 (P < 0.05), and cGMP specific phosphodiesterase 5 (P < 0.05). Lower mRNA levels for endothelial nitric oxide synthase occurred in the ipsilateral lung (P < 0.05). CONCLUSIONS: Experimental DH in fetal rabbits disrupted transcription of genes implicated in lung growth and function. Similarities with the human disease make this model appropriate for investigation of new prenatal therapies.

Elastin accumulation is regulated at the level of degradation by macrophage metalloelastase (MMP-12) during experimental liver fibrosis.

UNLABELLED: Elastin has been linked to maturity of liver fibrosis. To date, the regulation of elastin secretion and its degradation in liver fibrosis has not been characterized. The aim of this work was to define elastin accumulation and the role of the paradigm elastase macrophage metalloelastase (MMP-12) in its turnover during fibrosis. Liver fibrosis was induced by either intraperitoneal injections of carbon tetrachloride (CCl(4) ) for up to 12 weeks (rat and mouse) or oral administration of thioacetamide (TAA) for 1 year (mouse). Elastin synthesis, deposition, and degradation were investigated by immunohistochemistry, quantitative polymerase chain reaction (qPCR), western blotting, and casein zymography. The regulation of MMP-12 elastin degradation was defined mechanistically using CD11b-DTR and MMP-12 knockout mice. In a CCl(4) model of fibrosis in rat, elastin deposition was significantly increased only in advanced fibrosis. Tropoelastin expression increased with duration of injury. MMP-12 protein levels were only modestly changed and in coimmunoprecipitation experiments MMP-12 was bound in greater quantities to its inhibitor TIMP-1 in advanced versus early fibrosis. Immunohistochemistry and macrophage depletion experiments indicated that macrophages were the sole source of MMP-12. Exposure of CCl(4) in MMP-12(-/-) mice led to a similar degree of overall fibrosis compared to wildtype (WT) but increased perisinusoidal elastin. Conversely, oral administration of TAA caused both higher elastin accumulation and higher fibrosis in MMP-12(-/-) mice compared with WT. CONCLUSION: Elastin is regulated at the level of degradation during liver fibrosis. Macrophage-derived MMP-12 regulates elastin degradation even in progressive experimental liver fibrosis. These observations have important implications for the design of antifibrotic therapies.

Elastomeric polypeptides.

Elastomeric polypeptides are very interesting biopolymers and are characterized by rubber-like elasticity, large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Their useful properties have motivated their use in a wide variety of materials and biological applications. This chapter focuses on elastin and resilin - two elastomeric biopolymers - and the recombinant polypeptides derived from them (elastin-like polypeptides and resilin-like polypeptides). This chapter also discusses the applications of these recombinant polypeptides in the fields of purification, drug delivery, and tissue engineering.

TGF-beta 1 is a potential regulator of vaginal tropoelastin production.

INTRODUCTION AND HYPOTHESIS: Our aims were to correlate transforming growth factor (TGF)-ß1 and elastin mRNA expression in the vagina of women and to measure the effects of TGF-ß1 on vaginal smooth muscle cell (SMC) proliferation and tropoelastin production. METHODS: Vaginal walls were sampled in women (n = 20). TGF-ß1 and elastin mRNA expression was assessed by RT-PCR. SMC cultures were performed from vaginal wall biopsies. SMC were incubated with TGF-ß1, and cell proliferation was assessed by MTT-assay. Tropoelastin production was measured by the Fastin Elastin Assay. RESULTS: There was a significant positive correlation between TGF-ß1 and elastin mRNA (r = 0.784, P < 0.01). SMC proliferation was significantly increased by 10 ng/mL TGF-ß1 [relative cell number, mean ± SD, 198% ± 32% of control (P = 0.01)]. Tropoelastin production was significantly increased by TGF-ß1 [mean ± SD, 645% ± 180% of control (P = 0.01)]. CONCLUSIONS: There is a positive correlation between TGF-ß1 and elastin mRNA expression in the vaginal wall. In vitro, TGF-ß1 increases vaginal tropoelastin production in vaginal SMC.

Levormeloxifene inhibits vaginal tropoelastin and transforming growth factor beta 1 production.

PURPOSE: To measure the effects of levormeloxifene on vaginal smooth muscle cell (SMC) proliferation, tropoelastin and transforming growth factor (TGF)-ß1 production. METHODS: Primary SMC cultures were performed from vaginal wall biopsies. SMC were incubated with levormeloxifene (0.1 µM, 1 µM), in 96-well plates and cell proliferation was assessed by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazoliumbromide (MTT) assay at 24 hours. Tropoelastin production was measured by the Fastin Assay kit and TGF-ß1 levels were assessed by ELISA. RESULTS: SMC proliferation was significantly increased by levormeloxifene [relative cell number, mean ± SE, levormeloxifene 0.1 µM 130 ± 13% of control (P=NS), 1 µM 151 ± 19% of control (P<0.05)]. Tropoelastin production was significantly decreased by levormeloxifene [mean ± SE, levormeloxifene 0.1 µM 75 ± 4% of control (P=NS), 1 µM 64 ± 2% of control (P<0.05)]. In addition, TGF-ß1 production was significantly decreased [mean ± SE, levormeloxifene 0.1 µM 79 ± 11% of control (P=NS), 1 µM 72 ± 14% of control (P<0.05)]. CONCLUSIONS: Levormeloxifene increases vaginal SMC proliferation, inhibits tropoelastin and TGF- ß1 production.

Dexamethasone normalizes aberrant elastic fiber production and collagen 1 secretion by Loeys-Dietz syndrome fibroblasts: a possible treatment?

Loeys-Dietz syndrome (LDS) is an autosomal dominant connective tissue disorder characterized by facial dysmorphism, cleft palate, dilation of the aortic arch, blood vessel tortuosity and a high risk of aortic dissection. It is caused by mutations in the transforming growth factor ß-receptor 1 and 2 (TGFß-R1 and TGFß-R2) genes. Fibroblasts derived from 12 Loeys-Dietz syndrome patients, six with TGFB-R1 mutations and six with TGFB-R2 mutations, were analyzed using RT-PCR, biochemical assays, immunohistochemistry and electron microscopy for production of elastin, fibrillin 1, fibulin 1 and fibulin 4 and deposition of collagen type I. All LDS fibroblasts with TGFß-R1 mutations demonstrated decreased expression of elastin and fibulin 1 genes and impaired deposition of elastic fibers. In contrast, fibroblasts with TGFß-R2 mutations consistently demonstrated intracellular accumulation of collagen type I in the presence of otherwise normal elastic fiber production. Treatment of the cell cultures with dexamethasone induced remarkable upregulation in the expression of tropoelastin, fibulin 1- and fibulin 4-encoding mRNAs, leading to normalization of elastic fiber production in fibroblasts with TGFß-R1 mutations. Treatment with dexamethasone also corrected the abnormal secretion of collagen type I from fibroblasts with TGFß-R2 gene mutations. As the organogenesis-relevant elastic fiber production occurs exclusively in late fetal and early neonatal life, these findings may have implications for treatment in early life. Further studies are required to determine if dexamethasone treatment of fetuses prenatally diagnosed with LDS would prevent or alleviate the connective tissue and vascular defects seen in this syndrome.

Protective effect of pomegranate-derived products on UVB-mediated damage in human reconstituted skin.

Solar ultraviolet (UV) radiation, particularly its UVB (290-320 nm) component, is the primary cause of many adverse biological effects including photoageing and skin cancer. UVB radiation causes DNA damage, protein oxidation and induces matrix metalloproteinases (MMPs). Photochemoprevention via the use of botanical antioxidants in affording protection to human skin against UVB damage is receiving increasing attention. Pomegranate, from the tree Punica granatum, contains anthocyanins and hydrolysable tannins and possesses strong antioxidant and anti-tumor-promoting properties. In this study, we determined the effect of pomegranate-derived products--POMx juice, POMx extract and pomegranate oil (POMo)--against UVB-mediated damage using reconstituted human skin (EpiDerm(TM) FT-200). EpiDerm was treated with POMx juice (1-2 microl/0.1 ml/well), POMx extract (5-10 microg/0.1 ml/well) and POMo (1-2 microl/0.1 ml/well) for 1 h prior to UVB (60 mJ/cm(2)) irradiation and was harvested 12 h post-UVB to assess protein oxidation, markers of DNA damage and photoageing by Western blot analysis and immunohistochemistry. Pretreatment of Epiderm with pomegranate-derived products resulted in inhibition of UVB-induced (i) cyclobutane pyrimidine dimers (CPD), (ii) 8-dihydro-2'-deoxyguanosine (8-OHdG), (iii) protein oxidation and (iv) proliferating cell nuclear antigen (PCNA) protein expression. We also found that pretreatment of Epiderm with pomegranate-derived products resulted in inhibition of UVB-induced (i) collagenase (MMP-1), (ii) gelatinase (MMP-2, MMP-9), (iii) stromelysin (MMP-3), (iv) marilysin (MMP-7), (v) elastase (MMP-12) and (vi) tropoelastin. Gelatin zymography revealed that pomegranate-derived products inhibited UVB-induced MMP-2 and MMP-9 activities. Pomegranate-derived products also caused a decrease in UVB-induced protein expression of c-Fos and phosphorylation of c-Jun. Collectively, these results suggest that all three pomegranate-derived products may be useful against UVB-induced damage to human skin.

High copper levels and increased elastolysis in a patient with cutis marmorata teleangiectasia congenita.

Cutis marmorata telangiectatica congenita (CMTC) is a rare cutaneous vascular disease presenting at birth with levido reticularis, phlebectasia, and telangiectasia, often accompanied by skin ulcerations. Extra-dermal vascular anomalies can be also detected in 30-70% of described cases. The pathomechanism responsible for development of these phenotypic changes is not well understood. Here, we report on a 16-month-old boy with CMTC, generalized vascular abnormalities and severe, nitric oxide sensitive, pulmonary hypertension associating with markedly elevated level of blood copper. Results of laboratory investigations indicated that primary cultures (passage one) of dermal fibroblasts derived from this patient were capable of normal synthesis of tropoelastin, but their net deposition of mature elastic fibers was significantly diminished as compared with cultures of normal fibroblasts. Because the low net deposition of elastin was reversed when 1 mg/ml of alpha1-antitrypsin was added to the media, we conclude that heightened elastolysis by endogenous serine proteinase's is responsible for the low net elastogenesis by CMTC fibroblasts. Since simultaneous addition of 30 microM CuSO(4) and 1 mg/ml alpha1-antitrypsin abolished the beneficial effect of this serine proteinase's inhibitor, we concluded that this may be due to copper-dependent inactivation of alpha1-antitrypsin. Our data suggest that a high level of free copper may constitute a major triggering factor contributing to the development of the CMTC phenotype.

Elastic fibers reconstructed using adenovirus-mediated expression of tropoelastin and tested in the elastase model of abdominal aortic aneurysm in rats.

OBJECTIVE: An adenoviral vector carrying a recombinant tropoelastin (TE) gene with a Green Fluorescent Protein (GFP) tag adenoviral tropoelastin green fluorescent protein (AdTE-GFP) was transferred to aortic vascular smooth muscle cells (VSMCs) for studying the expression of recombinant elastin in vitro and the reconstruction of elastic fibers in vivo in experimental abdominal aortic aneurysm (AAA). METHODS: The AAAs were induced in rats by perfusing the arteries with porcine pancreatic elastase, and after AAA formation, adenoviral vectors were perfused directly into the aneurysmal lumen. VSMCs transfected with AdTE-GFP in vitro and in vivo were detected by fluorescence microscopy. The TE mRNA levels and the level of recombinant elastin expression of AdTE-GFP transfected VSMCs in vitro (at 1, 3, and 5 days) and in vivo (at 2 and 4 weeks) were compared by real-time reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. The aortic diameters (AD) of the aneurysms were measured at three time points (immediately, 2 weeks, and 4 weeks post-perfusion) and comparisons were made among the AdTE-GFP transfected group, an empty adenovirus (AdNull) transfected group, and a phosphate buffered saline (PBS) perfused group. Formation of new elastic fibers in vivo was assessed by histologic analysis. RESULTS: AdTE-GFP transfection reversed AAA formation (mean +/- standard error), with the controls showing increased ADs (a 48.50 +/- 16.55% increase for the PBS perfusion group and a 39.84 +/- 15.59% increase for the AdNull treated group) and the AdTE-GFP transfected group showing a decreased AD (23.04 +/- 14.49%, P < .01). Histological studies showed that the AdTE-GFP transfected group also had reconstructed elastic fibers in the aneurysmal wall. Real-time PCR for TE mRNA demonstrated a significant increase upon transfection of AdTE-GFP in vitro and in vivo. Western blot analysis for GFP demonstrated elastin-GFP expression only upon transfection of AdTE-GFP, although the amount of elastin-GFP protein tended to be lower in vivo than in vitro. Elastin von-Giesson stain combined with GFP antibody immunohistochemistry demonstrated new elastic fibers in the transfected aneurysmal VSMCs. CONCLUSION: VSMCs were transfected efficiently with a special AdTE-GFP vector, enabling recombinant elastin to be produced in these VSMCs in vitro and in vivo. This expression of a recombinant elastin and the related reconstruction of elastic fibers within the aneurysmal tissue appeared to prevent or reverse the aneurysm dilatation.

EGF antagonizes TGF-beta-induced tropoelastin expression in lung fibroblasts via stabilization of Smad corepressor TGIF.

We previously reported that neutrophil elastase (NE) downregulates transforming growth factor-beta (TGF-beta)-maintained tropoelastin mRNA levels in lung fibroblasts through transactivation of the epidermal growth factor (EGF) receptor (EGFR)/Mek/Erk pathway, which is dependent on the NE-initiated release of soluble EGFR ligands. In the present study, we investigated the mechanism by which EGF downregulates tropoelastin expression. We found that EGF downregulates tropoelastin expression through inhibition of TGF-beta signaling. We show that EGF does not prevent the TGF-beta-induced nuclear accumulation of Smad2/3; rather, EGF stabilizes the short-lived Smad transcriptional corepressor TG-interacting factor (TGIF) via EGFR/Mek/Erk-mediated phosphorylation of TGIF. Elevation of TGIF levels, either by TGIF overexpression or prevention of TGIF degradation, is sufficient to inhibit TGF-beta-induced tropoelastin expression. Moreover, TGIF is essential for EGF-mediated downregulation of tropoelastin expression, inasmuch as small interfering RNA knockdown of TGIF blocked EGF-induced downregulation of tropoelastin. Finally, we demonstrated that NE treatment, which releases EGF-like growth factors, causes stabilization of TGIF through the EGFR/Mek/Erk pathway. These results suggest that EGFR/Mek/Erk signaling specifically antagonizes the proelastogenic action of TGF-beta in lung fibroblasts by stabilizing the Smad transcriptional corepressor TGIF.

The dissection of human tropoelastin: from the molecular structure to the self-assembly to the elasticity mechanism.

After a historical introduction the authors describe their most recent results on the structure, assembly and elasticity of elastin. Recent results obtained by analyzing the conformation of polypeptide sequences encoded by the single exons of human tropoelastin demonstrated the presence of labile conformations such as poly-proline II helix (PPII) and beta-turns whose stability is strongly dependent on the microenvironment. Stable, periodic structures, such as alpha-helices, are only present in the poly-alanine cross-linking domains. These findings give a strong experimental basis to the understanding of the molecular mechanism of elasticity of elastin. In particular, they strongly support the description of the native relaxed state of the protein in terms of trans-conformational equilibria between extended and folded structures as previously proposed [Int. J. Biochem. Cell. Biol. 31 (1999) 261]. The same polypeptide sequences have been analyzed for their ability to coacervate and to self-assembly. Although the great majority of them were shown to be able to adopt more or less organized structures, only a few were indeed able to coacervate. Studies carried out by transmission electron microscopy showed the polypeptides to adopt a variety of supramolecular structures going from a filamentous organization (typical of elastin) to amyloid-like fibers. On the whole, the results obtained gave significant insight to the roles played by specific polypeptide sequences in self-assembly and possibly in elasticity.

The tissue distribution of murine Abcc6 (Mrp6) during embryogenesis indicates that the presence of Abcc6 in elastic tissues is not required for elastic fiber assembly.

Mutations in the gene coding for the ABC transporter, ABCC6, in humans cause Pseudoxanthoma elasticum, which is characterized by the deposition of aberrant elastic fibers. To investigate whether the presence of ABCC6 in tissues synthesizing elastin is required for elastin deposition and elastic fiber assembly, we have compared the steady-state levels and tissue distribution of Abcc6 and tropoelastin mRNAs during mouse embryogenesis. Whereas tropoelastin mRNA levels rose during embryogenesis and were the highest in neonatal mice, Abcc6 mRNA levels remained constantly low throughout embryogenesis. In some tissues, both Abcc6 and tropoelastin mRNA were detected. However, Abcc6 mRNA and protein were not detected in neonatal aorta and arteries, which produce large amounts of elastin indicating that the presence of Abcc6 in elastic tissues is not required for elastic fiber assembly.

[Modulation of tropoelastin expression in cultured human dermal fibroblasts by heat shock].

OBJECTIVE: To observe the effect of heat shock on tropoelastin mRNA and protein expression in cultured human dermal fibroblasts and to elucidate the possible role of heat shock in the development of solar elastosis in human skin. METHODS: Primary cultured human dermal fibroblasts were incubated in 43 degrees C water bath for 30 minutes, then returned to 37 degrees C, 5%(volume fraction) CO(2) atmosphere normal culture condition. The cells were harvested at hour 24 and 48 after heat treatment respectively. Total RNA was extracted from cell lysis and tropoelastin mRNA level was measured by Northern blot assay. Tropoelastin protein level in cultured supernatant was measured by Western blot assay. RESULTS: At hour 24 after heat treatment, the level of tropoelastin mRNA was enhanced to (163+/-12)% of control group (P<0.05). It was increased further to (221+/-22)% of control group at hour 48 after heat treatment (P<0.05). Similarly, the tropoelastin protein level was also increased to (149+/-12)% (P<0.05) at hour 24, and to (783+/-10)% (P<0.05) at hour 48 after heat shock as compared with control group. CONCLUSION: Heat shock could up-regulate tropoelastin mRNA and protein expression in primary cultured human dermal fibroblasts, and the over-expression of tropoelastin might play some roles in the development of solar elastosis in photoaged skin.