RESUMO
Transposable elements modify human genome by inserting into new loci or by mediating homology-, microhomology-, or homeology-driven DNA recombination or repair, resulting in genomic structural variation. Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal neonatal developmental lung disorder caused by point mutations or copy-number variant (CNV) deletions of FOXF1 or its distant tissue-specific enhancer. Eighty-five percent of 45 ACDMPV-causative CNV deletions, of which junctions have been sequenced, had at least one of their two breakpoints located in a retrotransposon, with more than half of them being Alu elements. We describe a novel â¼35 kb-large genomic instability hotspot at 16q24.1, involving two evolutionarily young LINE-1 (L1) elements, L1PA2 and L1PA3, flanking AluY, two AluSx, AluSx1, and AluJr elements. The occurrence of L1s at this location coincided with the branching out of the Homo-Pan-Gorilla clade, and was preceded by the insertion of AluSx, AluSx1, and AluJr. Our data show that, in addition to mediating recurrent CNVs, L1 and Alu retrotransposons can predispose the human genome to formation of variably sized CNVs, both of clinical and evolutionary relevance. Nonetheless, epigenetic or other genomic features of this locus might also contribute to its increased instability.
Assuntos
Cromossomos Humanos Par 16/genética , Variações do Número de Cópias de DNA , Instabilidade Genômica , Síndrome da Persistência do Padrão de Circulação Fetal/genética , Elementos Alu , Evolução Molecular , Fatores de Transcrição Forkhead/genética , Predisposição Genética para Doença , Humanos , Elementos Nucleotídeos Longos e Dispersos , Linhagem , Mutação PuntualRESUMO
We hypothesized that ablation of smooth muscle α-actin (SM α-A), a contractile-cytoskeletal protein expressed in airway smooth muscle (ASM) cells, abolishes ASM shortening capacity and decreases lung stiffness. In both SM α-A knockout and wild-type (WT) mice, airway resistance (Raw) determined by the forced oscillation technique rose in response to intravenous methacholine (Mch). However, the slope of Raw (cmH(2)O·ml(-1)·s) vs. log(2) Mch dose (µg·kg(-1)·min(-1)) was lower (P = 0.007) in mutant (0.54 ± 0.14) than in WT mice (1.23 ± 0.19). RT-PCR analysis performed on lung tissues confirmed that mutant mice lacked SM α-A mRNA and showed that these mice had robust expressions of both SM γ-A mRNA and skeletal muscle (SKM) α-A mRNA, which were not expressed in WT mice, and an enhanced SM22 mRNA expression relative to that in WT mice. Compared with corresponding spontaneously breathing mice, mechanical ventilation-induced lung mechanical strain increased the expression of SM α-A mRNA in WT lungs; in mutant mice, it augmented the expressions of SM γ-A mRNA and SM22 mRNA and did not alter that of SKM α-A mRNA. In mutant mice, the expression of SM γ-A mRNA in the lung during spontaneous breathing and its enhanced expression following mechanical ventilation are consistent with the likely possibility that in the absence of SM α-A, SM γ-A underwent polymerization and interacted with smooth muscle myosin to produce ASM shortening during cholinergic stimulation. Thus our data are consistent with ASM in mutant mice experiencing compensatory mechanisms that modulated its contractile muscle capacity.
Assuntos
Actinas/genética , Actinas/metabolismo , Pulmão/metabolismo , Pulmão/fisiologia , Contração Muscular/fisiologia , Músculo Liso/metabolismo , Músculo Liso/fisiologia , Resistência das Vias Respiratórias/efeitos dos fármacos , Resistência das Vias Respiratórias/genética , Resistência das Vias Respiratórias/fisiologia , Animais , Proteínas Contráteis/genética , Proteínas Contráteis/metabolismo , Pulmão/efeitos dos fármacos , Cloreto de Metacolina/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas dos Microfilamentos/genética , Proteínas dos Microfilamentos/metabolismo , Contração Muscular/efeitos dos fármacos , Contração Muscular/genética , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiologia , Miócitos de Músculo Liso/efeitos dos fármacos , Miócitos de Músculo Liso/metabolismo , Miócitos de Músculo Liso/fisiologia , RNA Mensageiro/genética , Respiração Artificial/métodos , Miosinas de Músculo Liso/efeitos dos fármacos , Miosinas de Músculo Liso/genética , Miosinas de Músculo Liso/metabolismo , Miosinas de Músculo Liso/fisiologiaRESUMO
Desmin is a structural protein that is expressed in smooth muscle cells of both airways and alveolar ducts. Therefore, desmin could be well situated to participate in passive and contractile force transmission in the lung. We hypothesized that desmin modulates lung compliance, lung recoil pressure, and airway contractile response. To test this hypothesis, respiratory system complex impedance (Zin,rs) at different positive end-expiratory pressure (PEEP) levels and quasi-static pressure-volume data were obtained in desmin-null and wild-type mice at baseline and during methacholine administration. Airways and lung tissue properties were partitioned by fitting Zin,rs to a constant-phase model. Relative to controls, desmin-null mice showed 1) lower values for lung stiffness and recoil pressure at baseline and induced airway constriction, 2) greater negative PEEP dependence of H and airway resistance under baseline conditions and cholinergic stimulation, and 3) airway hyporesponsiveness. These results demonstrate that desmin is a load-bearing protein that stiffens the airways and consequently the lung and modulates airway contractile response.
Assuntos
Resistência das Vias Respiratórias/fisiologia , Desmina/fisiologia , Pulmão/fisiologia , Animais , Desmina/deficiência , Desmina/genética , Elasticidade , Complacência Pulmonar/efeitos dos fármacos , Complacência Pulmonar/fisiologia , Camundongos , Camundongos Knockout , Respiração com Pressão Positiva , Mecânica Respiratória/efeitos dos fármacos , Mecânica Respiratória/fisiologiaRESUMO
The clinical effects of treatment with beta-adrenoceptor (beta-AR) agonists and antagonists in heart failure vary with duration of therapy, as do the effects of beta-AR agonists in asthma. Therefore, we hypothesized that chronic effects of "beta-blockers" in asthma may differ from those observed acutely. We tested this hypothesis in an antigen (ovalbumin)-driven murine model of asthma. Airway resistance responses (Raw) to the muscarinic agonist methacholine were measured by using the forced oscillation technique. In comparison with nontreated asthmatic mice, we observed that: (i) The beta-AR antagonists nadolol or carvedilol, given as a single i.v. injection (acute treatment) 15 min before methacholine, increased methacholine-elicited peak Raw values by 33.7% and 67.7% (P < 0.05), respectively; when either drug was administered for 28 days (chronic treatment), the peak Raw values were decreased by 43% (P < 0.05) and 22.9% (P < 0.05), respectively. (ii) Chronic treatment with nadolol or carvedilol significantly increased beta-AR densities in lung membranes by 719% and 828%, respectively. (iii) Alprenolol, a beta-blocker with partial agonist properties at beta-ARs, behaved as a beta-AR agonist, and acutely reduced peak Raw value by 75.7% (P < 0.05); chronically, it did not alter Raw. (iv) Salbutamol, a beta-AR partial agonist, acutely decreased peak Raw by 41.1%; chronically, it did not alter Raw. (v) None of the beta-blockers produced significant changes in eosinophil number recovered in bronchoalveolar lavage. These results suggest that beta-AR agonists and beta-blockers with inverse agonist properties may exert reciprocating effects on cellular signaling dependent on duration of administration.
Assuntos
Agonistas Adrenérgicos beta/farmacologia , Antagonistas Adrenérgicos beta/farmacologia , Asma/tratamento farmacológico , Receptores Adrenérgicos beta/efeitos dos fármacos , Agonistas Adrenérgicos beta/administração & dosagem , Agonistas Adrenérgicos beta/uso terapêutico , Antagonistas Adrenérgicos beta/administração & dosagem , Antagonistas Adrenérgicos beta/uso terapêutico , Animais , Asma/fisiopatologia , Líquido da Lavagem Broncoalveolar , Ligantes , Camundongos , Camundongos Endogâmicos BALB C , Transdução de SinaisRESUMO
Airway dysfunction in asthma is characterized by hyperresponsiveness, heterogeneously narrowed airways, and closure of airways. To test the hypothesis that airway constriction in ovalbumin (OVA)-sensitized OVA-intranasally challenged (OVA/OVA) mice produces mechanical responses that are similar to those reported in asthmatic subjects, respiratory system resistance (Rrs) and elastance (Edyn,rs) spectra were obtained in OVA/OVA and control mice during intravenous methacholine (MCh) infusions. In control mice, MCh at 1,700 microg x kg(-1) x min(-1) produced 1) a 495 and 928% increase of Rrs at 0.5 Hz and 19.75 Hz, respectively, 2) a 33% rise in Edyn,rs at 0.5 Hz, and 3) a mild frequency (f)-dependent increase of Edyn,rs. The same MCh dose in OVA/OVA mice produced 1) elevations of Rrs at 0.5 Hz and 19.75 Hz of 1,792 and 774%, respectively, 2) a 390% rise in Edyn,rs at 0.5 Hz, and 3) marked f-dependent increases of Edyn,rs. During constriction, the f dependence of mechanics in control mice was consistent with homogeneous airway narrowing; however, in OVA/OVA mice, f dependence was characteristic of heterogeneously narrowed airways, closure of airways, and airway shunting. These mechanisms amplify the pulmonary mechanical responses to constrictor stimuli at physiological breathing rates and have important roles in the pathophysiology of human asthma.