RESUMO
BACKGROUND: Neutrophil elastase plays an important role in skin inflammation induced by neutrophil infiltration. Elafin is an inducible elastase inhibitor expressed by keratinocytes, and is known to be involved in pathogenesis of neutrophilic skin disorders such as psoriasis. METHODS: Immunohistochemical studies of elafin expression in the cases of vasculitis were performed. Induction of elafin expression in cultured vascular cells and its effect on neutrophil migration were studied in vitro. RESULTS: A positive immunoreactivity was detected in polyarteritis nodosa, giant cell arteritis and Schönlein-Henoch purpura, but no immunoreactivity was found in Churg-Strauss syndrome. Elafin expression in cultured venous endothelial cells and arterial smooth muscle cells was undetectable, but induced by interleukin-1ß (IL-1ß) and IL-8. Elafin inhibited the elastin peptide-induced neutrophil chemotaxis at the concentration of 10(-8) -10(-5) mol/L. CONCLUSION: Elafin deposition induced by cytokines (IL-1ß or IL-8) will be an important regulator for the progress of leucocytoclastic vasculitis by functioning as an inhibitor for neutrophil chemotaxis as well as for vascular elastin degradation.
Assuntos
Elafina/metabolismo , Neutrófilos/patologia , Pele/irrigação sanguínea , Túnica Íntima/metabolismo , Vasculite/metabolismo , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Células Cultivadas , Quimiotaxia de Leucócito , Citocinas/fisiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
The age- and gender-related changes in extracellular matrix components (elastin, elastin cross-links, fibrillin, collagen and glycoprotein) and mineral components (calcium, Ca; phosphorus, P) in human lumbar yellow ligaments were investigated using samples obtained from surgical specimens. The mineral (Ca and P) contents increased with ageing (r = 0.703 and r = 0.772, respectively), whereas the contents of matrix components tended to decrease with ageing (elastin r = -0.261, elastin cross-links r = -0.213, fibrillin r = 0.494; collagen r = -0.322 and glycoprotein r = -0.143). Comparison of the male and female groups revealed that the ligament elastin content and elastin cross-links decreased in the male group, whereas the ligament collagen content decreased in the female group significantly in an age-dependent manner (r = -0.788, r = -0.753 and r = -0.721, respectively). These findings demonstrate age- and gender-related changes in mineral and matrix components (especially elastin and collagen) in the lumbar yellow ligaments in the Japanese population. It is suggested that elastin and collagen metabolism in ligaments changes both with age and according to gender.
Assuntos
Envelhecimento/fisiologia , Ligamentos/química , Ligamentos/metabolismo , Caracteres Sexuais , Adulto , Idoso , Cálcio/metabolismo , Colágeno/metabolismo , Desmosina/metabolismo , Elastina/metabolismo , Feminino , Fibrilinas , Glicoproteínas/metabolismo , Humanos , Masculino , Proteínas dos Microfilamentos/metabolismo , Pessoa de Meia-Idade , Fósforo/metabolismo , Reprodutibilidade dos TestesRESUMO
Nitric oxide (NO), an endothelium-dependent relaxing factor, regulates relaxation, proliferation, and migration of smooth muscle cells (SMCs) and most likely attenuates developing vascular disease such as atherosclerosis. We investigated whether or not NO is associated with regulation of aortic elasticity. S-Nitrosoglutathione (GSNO), a NO donor, stimulated tropoelastin synthesis in cultured SMCs during both the quiescent and proliferating phases. The stimulation of tropoelastin synthesis was dose-dependent within 1-100 nM. Maximum stimulation was detected by treatment with 100 nM GSNO for 24 h. 8-Bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP), an exogenous cyclic GMP analog, also upregulated tropoelastin synthesis. Tropoelastin and lysyl oxidase mRNA expression, as assessed by Northern blot analysis, was also stimulated by GSNO. Administration of KT5823, a cyclic GMP-dependent protein kinase inhibitor, inhibited the GSNO-induced tropoelastin synthesis. These results indicate that the stimulatory effects of GSNO are due to cyclic GMP dependent protein kinase (PKG) activation by NO. In conclusion, NO seems to enhance aortic elasticity via tropoelastin and lysyl oxidase upregulation.
Assuntos
Elastina/biossíntese , Músculo Liso Vascular/metabolismo , Óxido Nítrico/fisiologia , Animais , Aorta/metabolismo , Arteriosclerose/etiologia , Arteriosclerose/metabolismo , Arteriosclerose/prevenção & controle , Divisão Celular/efeitos dos fármacos , Embrião de Galinha , GMP Cíclico/análogos & derivados , GMP Cíclico/farmacologia , Proteínas Quinases Dependentes de GMP Cíclico/fisiologia , Glutationa/análogos & derivados , Glutationa/farmacologia , Compostos Nitrosos/farmacologia , Proteína-Lisina 6-Oxidase/genética , RNA Mensageiro/análise , S-Nitrosoglutationa , Tropoelastina/biossíntese , Tropoelastina/genéticaRESUMO
To examine quantitative changes of elastin, fibrillin and collagen in abdominal aortic aneurysms, including ruptured abdominal aortic aneurysms (RAAA), inflammatory abdominal aortic aneurysms (IAAA) and abdominal aortic aneurysms (AAA) were measured. Items measured included the desmosine content of the aorta (desmosine 1) or of the elastin fraction (desmosine 2), fibrillin content in the aorta, hydroxyproline in the aorta, collagen percent and elastin percent, and were compared with control samples from the nonaneurysmal aortic segments. The elastin contents (desmosine 2) in RAAA, IAAA and AAA were significantly lower than those of controls. The content of the desmosine 2 from IAAA and AAA did not show a negative association with Ca. The fibrillin contents of the aorta from RAAA, IAAA and AAA were significantly higher than those of controls. The collagen content in the RAAA aorta was significantly higher than that of controls. There was a correlation of the ratio of fibrillin to elastin components (fibrillin/desmosine 1 or fibrillin/desmosine 2 or fibrillin/elastin%) and the ratio of collagen to elastin components (collagen/desmosine 1 or collagen/desmosine 2 or collagen/elastin%). These results indicated that increasing fibrillin and collagen might be a complementary result of decreasing elastin crosslinks in the aorta. This phenomenon was markedly in RAAA.
Assuntos
Aneurisma da Aorta Abdominal/metabolismo , Colágeno/metabolismo , Elastina/metabolismo , Proteínas dos Microfilamentos/metabolismo , Idoso , Idoso de 80 Anos ou mais , Fibrilinas , HumanosRESUMO
Elastic fibers consist of two morphologically distinct components: elastin and 10-nm fibrillin-containing microfibrils. During development, the microfibrils form bundles that appear to act as a scaffold for the deposition, orientation, and assembly of tropoelastin monomers into an insoluble elastic fiber. Although microfibrils can assemble independent of elastin, tropoelastin monomers do not assemble without the presence of microfibrils. In the present study, immortalized ciliary body pigmented epithelial (PE) cells were investigated for their potential to serve as a cell culture model for elastic fiber assembly. Northern analysis showed that the PE cells express microfibril proteins but do not express tropoelastin. Immunofluorescence staining and electron microscopy confirmed that the microfibril proteins produced by the PE cells assemble into intact microfibrils. When the PE cells were transfected with a mammalian expression vector containing a bovine tropoelastin cDNA, the cells were found to express and secrete tropoelastin. Immunofluorescence and electron microscopic examination of the transfected PE cells showed the presence of elastic fibers in the matrix. Biochemical analysis of this matrix showed the presence of cross-links that are unique to mature insoluble elastin. Together, these results indicate that the PE cells provide a unique, stable in vitro system in which to study elastic fiber assembly.
Assuntos
Corpo Ciliar/metabolismo , Proteínas Contráteis/metabolismo , Proteínas da Matriz Extracelular , Microfibrilas/metabolismo , Animais , Bovinos , Células Cultivadas , Condrócitos , Desmosina/análise , Tecido Elástico/metabolismo , Elastina/genética , Elastina/metabolismo , Matriz Extracelular/ultraestrutura , Fibrilinas , Imunofluorescência , Humanos , Técnicas In Vitro , Microfibrilas/ultraestrutura , Proteínas dos Microfilamentos/química , Microscopia Eletrônica , Fatores de Processamento de RNA , Transfecção , Tropoelastina/genética , Tropoelastina/metabolismoRESUMO
Elastin, an extracellular component of arteries, lung, and skin, is produced during fetal and neonatal growth. We reported previously that the cessation of elastin production is controlled by a posttranscriptional mechanism. Although tropoelastin pre-mRNA is transcribed at the same rate in neonates and adults, marked instability of the fully processed transcript bars protein production in mature tissue. Using RNase protection, we identified a 10-nucleotide sequence in tropoelastin mRNA near the 5' end of the sequences coded by exon 30 that interacts specifically with a developmentally regulated cytosolic 50-kDa protein. Binding activity increased as tropoelastin expression dropped, being low in neonatal fibroblasts and high in adult cells, and treatment with transforming growth factor beta1 (TGF-beta1), which stimulates tropoelastin expression by stabilizing its mRNA, reduced mRNA-binding activity. No other region of tropoelastin mRNA interacted with cellular proteins, and no binding activity was detected in nuclear extracts. The ability of the exon-30 element to control mRNA decay and responsiveness to TGF-beta1 was assessed by three distinct functional assays: (i) insertion of exon 30 into a heterologous gene conferred increased reporter activity after exposure to TGF-beta1; (ii) addition of excess exon 30 RNA slowed tropoelastin mRNA decay in an in vitro polysome degradation assay; and (iii) a mutant tropoelastin cDNA lacking exon 30, compared to wild-type cDNA, produced a stable transcript whose levels were not affected by TGF-beta1. These findings demonstrate that posttranscriptional regulation of elastin production in mature tissue is conferred by a specific element within the open reading frame of tropoelastin mRNA.
Assuntos
Processamento Pós-Transcricional do RNA , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Sequências Reguladoras de Ácido Nucleico , Fator de Crescimento Transformador beta/farmacologia , Tropoelastina/genética , Animais , Sequência de Bases , Citosol/metabolismo , Éxons , Regulação da Expressão Gênica , Pulmão/metabolismo , Dados de Sequência Molecular , Fases de Leitura Aberta , Ligação Proteica/efeitos dos fármacos , RNA Mensageiro/genética , Ratos , Ratos Sprague-Dawley , Mapeamento por RestriçãoRESUMO
BACKGROUND AND PURPOSE: Moyamoya disease is a progressive cerebrovascular occlusive disease that is rare in all ages but frequently presents in children. The etiology of the disease is unknown. We examined elastin gene transcripts and elastin synthesis in cultured arterial smooth muscle cells (SMCs) derived from moyamoya patients and compared them with those in SMCs from age-matched control subjects. METHODS: We used six cell strains from moyamoya patients and four from controls. The expression of elastin protein was observed by Western blot analysis and metabolic labeling with 3H-valine. Elastin gene transcripts were identified by Northern blot analysis. RESULTS: Elastin mRNA and protein levels were elevated in all SMCs from moyamoya patients compared with control SMCs. Although transforming growth factor-beta 1 (TGF-beta 1), a potent enhancer of the expression of elastin in arterial SMCs, upregulated elastin mRNA and protein levels in SMCs from both moyamoya patients and control subjects, the maximum levels of elastin synthesis and elastin gene transcripts in response to exogenous TGF-beta 1 were significantly greater in moyamoya SMCs than control SMCs. In addition, quiescent moyamoya SMCs secreted significantly more TGF-beta 1 into the culture medium than quiescent control SMCs (P < .01). CONCLUSIONS: Our findings suggest that moyamoya disease may result, at least in part, from an abnormal regulation of extracellular matrix metabolism that leads to increased steady state levels of elastin mRNA and elastin accumulation in the intimal thickening and that increased elastin accumulation is a stable marker of SMCs from patients with moyamoya disease.
Assuntos
Artérias/fisiopatologia , Elastina/genética , Elastina/metabolismo , Expressão Gênica , Doença de Moyamoya/genética , Doença de Moyamoya/metabolismo , Músculo Liso/fisiopatologia , Adolescente , Artérias/patologia , Northern Blotting , Western Blotting , Células Cultivadas , Criança , Pré-Escolar , Eletroforese em Gel de Poliacrilamida , Feminino , Humanos , Masculino , Doença de Moyamoya/patologia , Músculo Liso/patologia , Fator de Crescimento Transformador beta/metabolismo , Fator de Crescimento Transformador beta/farmacologiaAssuntos
Elastina/farmacologia , Oligopeptídeos/farmacologia , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina/farmacologia , Divisão Celular/efeitos dos fármacos , Elastina/análise , Fibroblastos/química , Fibroblastos/efeitos dos fármacos , Heparina/farmacologia , Humanos , Proteína Quinase C/fisiologia , Pele/química , Pele/citologia , Pele/efeitos dos fármacosRESUMO
Treatment with 80 nM monensin for 48 h resulted in impairment of tropoelastin secretion during the initial 6 h and subsequent reduction of tropoelastin synthesis from 18 to 48 h to one-tenth. The steady state level of tropoelastin mRNA started to decrease at 6 h and reached one-fifth of the control level by 48 h. A pulse-chase experiment after 24 h monensin treatment demonstrated that half of the accumulated tropoelastin in the cells was rapidly degraded within 120 min. These results indicate that the marked reduction in tropoelastin synthesis from 6 to 48 h treatment may be caused by both a reduction in the tropoelastin mRNA level and accelerated intracellular degradation of tropoelastin. Thus, monensin modulates tropoelastin expression through pretranslational and posttranslational mechanisms.
Assuntos
Monensin/farmacologia , Músculo Liso Vascular/metabolismo , Tropoelastina/genética , Tropoelastina/metabolismo , Animais , Northern Blotting , Células Cultivadas , Embrião de Galinha , Meios de Cultura/metabolismo , Ionóforos/farmacologia , Músculo Liso Vascular/citologia , Músculo Liso Vascular/efeitos dos fármacos , RNA Mensageiro/biossíntese , RNA Mensageiro/efeitos dos fármacos , Fatores de Tempo , Tropoelastina/efeitos dos fármacosRESUMO
Treatment of cultured smooth muscle cells with ascorbic acid resulted in an accumulation of tropoelastin in the culture medium in dose-dependent and exposure time-dependent manner under the condition in which collagen synthesis was stimulated 2-fold. The steady-state level of elastin mRNA was essentially unchanged, whereas collagen mRNA content increased 2-fold by ascorbic acid treatment. Newly synthesized tropoelastin was hydroxylated in the presence of ascorbic acid but was underhydroxylated in a scorbutic condition. Short pulse experiments showed that the secretion rate of tropoelastin was unaltered by ascorbic acid treatment. Pulse-chase experiment demonstrated that the level of fully hydroxylated tropoelastin in the medium of ascorbate-treated cells was greater than that of under-hydroxylated tropoelastin. These results indicate that accumulation of tropoelastin in the medium by ascorbic acid is related to an increased stability of hydroxylated tropoelastin and/or its impaired incorporation into insoluble elastin.
Assuntos
Ácido Ascórbico/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Tropoelastina/metabolismo , Actinas/genética , Animais , Células Cultivadas , Embrião de Galinha , Colágeno/genética , Meios de Cultura , Hidroxilação , Prolina/química , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Tropoelastina/química , Tropoelastina/genéticaRESUMO
The effect of heparin on elastin expression in the proliferating and quiescent phases of growth of smooth muscle cells was studied. Heparin stimulated elastin synthesis and its mRNA level 2-3 fold in the proliferating cells while it inhibited the cell proliferation. The inhibition of cell proliferation and the stimulation of elastin expression by heparin in the proliferating cells were mimicked by a potent protein kinase C antagonist, H-7, but not by H-89, W-7, and HA1004, suggesting that the effect of heparin is mediated by the inhibition of protein kinase C. In contrast, heparin inhibited elastin synthesis and its mRNA level slightly but exhibited no effect on cell proliferation in the growth-arrested cells. This result indicates that heparin reciprocally affects elastin expression depending on the growth state of smooth muscle cells. Heparin thus exerts a complex influence on elastin expression in smooth muscle cells.
Assuntos
Elastina/biossíntese , Inibidores Enzimáticos/farmacologia , Heparina/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/metabolismo , Proteína Quinase C/antagonistas & inibidores , Regulação para Cima/efeitos dos fármacos , 1-(5-Isoquinolinasulfonil)-2-Metilpiperazina , Animais , Western Blotting , Divisão Celular/efeitos dos fármacos , Divisão Celular/fisiologia , Células Cultivadas , Embrião de Galinha , Isoquinolinas/farmacologia , Músculo Liso Vascular/citologia , Piperazinas/farmacologia , Proteína Quinase C/metabolismo , RNA Mensageiro/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia , Tropoelastina/análise , Regulação para Cima/fisiologiaRESUMO
A study was made of the relationship between elastin expression and the proliferative state of chick vascular smooth-muscle cells. Confluent cells of primary culture brought to a quiescent state by the deprivation of serum for 72 h exhibited a 5-, 3.5- and 2-fold increase in elastin synthesis, elastin mRNA level and transcriptional activity of elastin gene respectively over those in the proliferative state. On re-addition of serum in serum-deprived culture, cells started to proliferate, and elastin synthesis, its mRNA level and transcription of the gene decreased to the level of a proliferative state within 24 h, indicating that elastin expression in smooth-muscle cells was controlled by their growth states at least in part at a transcriptional level. A comparable increase in elastin mRNA level was observed when the cell growth was arrested by suspension culture for 72 h. When the cells were synchronized at the G1/S phase with thymidine/hydroxyurea treatment, elastin expression at the G1/S phase was greater than that at the G2/M phase during cell cycling. Elastin mRNA level at the G0 phase brought about by serum-deprivation or suspension culture predominated over that at the G1/S phase during cell cycling. These results indicate that gene expression of elastin and cell cycle are tightly coupled, which is independent of the presence of serum or adhesive state, and that elastin expression could be a biochemical marker for the growth states of smooth-muscle cells.
Assuntos
Ciclo Celular/genética , Elastina/genética , Regulação da Expressão Gênica , Músculo Liso Vascular/metabolismo , Animais , Sangue , Células Cultivadas , Embrião de Galinha , Meios de Cultura , Músculo Liso Vascular/citologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Synthetic elastin peptides, VPGVG or its polymer (VPGVG)n, enhanced the proliferation of smooth muscle cells 1.5-fold during 48 h treatment at the concentrations over 10(-6) M or 1.0 microgram/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to one-third and one-half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin-specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.
Assuntos
Elastina/biossíntese , Homeostase/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Oligopeptídeos/farmacologia , Sequência de Aminoácidos , Animais , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Galinhas , Colágeno/biossíntese , Dados de Sequência Molecular , Músculo Liso Vascular/citologia , Músculo Liso Vascular/fisiologia , Oligopeptídeos/síntese química , RNA Mensageiro/biossínteseRESUMO
Significant amount of 45-kDa polypeptide was found to be present in the cultured medium of chick aortic smooth muscle cells. The polypeptide as well as tropoelastin (65-kDa) reacted with monoclonal antibody for tropoelastin. Pulse-chase experiments revealed that the relative density of the 45-kDa polypeptide to tropoelastin increased with chase periods. Partially purified radioactive tropoelastin (65-kDa) was converted to a 45-kDa polypeptide fragment in the test tube. The processing from the 65- to the 45-kDa polypeptide in the test tube was inhibited by ethylenediaminetetraacetic acid but not by N-ethylmaleimide and aminophenylmethylsulfonyl fluoride. These results indicate that the 45-kDa fragment is a degradation product of tropoelastin and that processing is mediated by enzymatic cleavages with metal proteinase. Fully hydroxylated tropoelastin treated with ascorbic acid was more resistant to the enzymes than underhydroxylated tropoelastin with scorbutic condition, suggesting that the structural stability of tropoelastin is also involved in the processing rate.
Assuntos
Elastina/análise , Músculo Liso Vascular/metabolismo , Fragmentos de Peptídeos/análise , Tropoelastina/metabolismo , Animais , Aorta , Ácido Ascórbico/farmacologia , Células Cultivadas , Embrião de Galinha , Meios de Cultivo Condicionados , Ácido Edético/farmacologia , Eletroforese em Gel de Poliacrilamida , Hidroxilação , Peso Molecular , Valina/metabolismoRESUMO
Tropoelastin expression in vascular smooth muscle cells during serial cell passages from the primary to the tertiary culture was studied. The level of tropoelastin was found to be greatly reduced as the number of cell passages increased. The translational activity and level of elastin mRNA were essentially unchanged throughout the cell passages. The reduction in tropoelastin expression was not due to the repetitive trypsin treatment nor to the prolyl hydroxylation level of the newly-synthesized elastin. A comparable decline in tropoelastin expression was also found with increasing cell division in the primary cultures plated at different cell densities. A pulse-chase experiment revealed that the newly-synthesized elastin in the tertiary culture degraded more rapidly than that in the primary culture. The culture medium harvested from the tertiary culture exhibited a higher tropoelastin-degrading activity than that from the primary culture in the test-tube. The degrading activity of the tertiary culture was inhibited by the addition of 1 mM ethylenediaminetetraacetic acid or 1 mM phenylmethylsulfonyl fluoride, but not by 1 mM N-ethylmaleimide. These results suggest that the reduction in tropoelastin expression during the cell passages from the primary to the tertiary culture is due to the enhanced tropoelastin-degrading activity of the tertiary culture. The transition to tropoelastin-degrading phenotype during cell passages may explain the biological mechanisms of smooth muscle cell migration from the media to the intima observed in the pathological conditions.
Assuntos
Músculo Liso Vascular/metabolismo , Tropoelastina/metabolismo , Animais , Divisão Celular , Células Cultivadas , Embrião de Galinha , Ácido Edético/farmacologia , Elastina/genética , Etilmaleimida/farmacologia , Hidroxilação , Fluoreto de Fenilmetilsulfonil/farmacologia , Prolina/metabolismo , Biossíntese de Proteínas , Processamento de Proteína Pós-Traducional , RNA Mensageiro/metabolismo , Fatores de Tempo , Tripsina/metabolismoRESUMO
Heparin is a potent inhibitor of smooth muscle cell proliferation. It reduced the level of type I collagen by one-half in culture medium of smooth muscle cells, whereas it increased the type I collagen expression 4-fold in the cell layer compartment under the conditions where it inhibited cell proliferation. No significant change in the level of prolyl hydroxylation in the newly synthesized type I procollagen or steady-state levels of pro alpha 1 (I) and pro alpha 2 (I) collagen mRNAs was detected after heparin treatment. Short-pulse and pulse-chase experiments revealed that heparin inhibited the secretion of type I procollagen and stimulated the accumulation of type I collagen in the extracellular space. These results suggest that heparin could modulate type I collagen expression at a posttranslational level. The modulation appeared to be closely related with its inhibitory effect on cell proliferation via two different mechanisms: the inhibition of the secretion of type I procollagen and stabilization of type I collagen in the cell layer. Heparin thus appears to be a multifunctional modulator for cell proliferation and the expression of type I collagen in vascular smooth muscle cells.
Assuntos
Colágeno/biossíntese , Regulação da Expressão Gênica , Heparina/farmacologia , Músculo Liso Vascular/metabolismo , Pró-Colágeno/metabolismo , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Animais , Aorta/citologia , Aorta/efeitos dos fármacos , Aorta/metabolismo , Northern Blotting , Divisão Celular , Células Cultivadas , Embrião de Galinha , Relação Dose-Resposta a Droga , Cinética , Músculo Liso Vascular/citologia , Músculo Liso Vascular/efeitos dos fármacos , Pró-Colágeno/biossíntese , RNA Mensageiro/análise , RNA Mensageiro/biossíntese , RNA Mensageiro/metabolismoRESUMO
Minoxidil was found to inhibit the proliferation of smooth muscle cells in the proliferating phase, but not in the quiescent phase. Treatment of proliferating or quiescent cells with minoxidil resulted in a dose- and time-dependent stimulation of elastin synthesis specifically. Maximum stimulation (fourfold) occurred in cells treated with 1 mM minoxidil for 48 h. The stimulation of elastin synthesis was accompanied by a proportional increase in elastin mRNA level, and it was partially prevented by a K+ channel blocker (tetraethylammonium) and completely prevented by high K+ salt (0.1 M). Minoxidil had no significant effect on the extent of prolyl hydroxylation in newly synthesized elastin. These results indicate that minoxidil stimulates elastin synthesis at a pretranslational level by a mechanism unrelated to cell proliferation but one that may involve K+ efflux. As a pharmacological agent capable of stimulating elastin expression, minoxidil would be a useful drug for the treatment of abnormal elastin metabolism.
Assuntos
Elastina/biossíntese , Minoxidil/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/enzimologia , Actinas/biossíntese , Actinas/genética , Aminopiridinas/farmacologia , Animais , Aorta/citologia , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Embrião de Galinha , Relação Dose-Resposta a Droga , Elastina/genética , Expressão Gênica , Hidroxilação , Potássio/farmacologia , Pró-Colágeno/biossíntese , Pró-Colágeno/genética , Prolina/metabolismo , RNA Mensageiro/análise , Tetraetilamônio , Compostos de Tetraetilamônio/farmacologia , Tropoelastina/metabolismoRESUMO
Effects of two major potent vasoconstrictors, angiotensin II and platelet-derived growth factor, on elastin expression in cultured chick embryonic arterial smooth muscle cells were studied. Platelet-derived growth factor exhibited no effect on elastin synthesis nor its mRNA level but stimulated (1.5-fold) cell proliferation slightly. Angiotensin II inhibited elastin synthesis dose- and time-dependent manner with a maximum suppression of sixty percent of control at a concentration of 10 microM for 18 h treatment. The suppression was accompanied with a comparable decrease in elastin mRNA level. The inhibition was blocked by addition of Sar1,Ala8-angiotensin II and 8-bromo-cGMP. It showed no effect on cell proliferation. Angiotensin II appears to inhibit elastin synthesis through the interaction with its receptor and the modulation of intracellular Ca2+ level. Thus angiotensin II, not platelet-derived growth factor, can exert a profound effect on the extracellular matrix composition in arterial walls, leading to an arterial change in hypertension or atherosclerosis.