RESUMO Objetivo: Descrever um modelo murino de enfisema induzido por exposição a fumaça de cigarro (FC) e instilação de elastase pancreática porcina (EPP). Métodos: Trinta e oito camundongos C57BL/6 foram aleatoriamente divididos em quatro grupos: controle (uma instilação intranasal de solução salina a 0,9%); EPP (duas instilações intranasais de EPP); FC (exposição a FC durante 60 dias) e FC + EPP (duas instilações intranasais de EPP + exposição a FC durante 60 dias). No fim do protocolo experimental, todos os animais foram anestesiados e traqueostomizados para o cálculo de parâmetros de mecânica respiratória. Em seguida, todos os animais foram sacrificados e seus pulmões foram removidos para a medição da intercepção linear média (Lm) e a determinação do número de células imunorreativas a antígeno macrofágico (MAC)-2, metaloproteinase da matriz (MMP)-12 e glicoproteína glicosilada de 91 kDa (gp91phox) no parênquima pulmonar distal e na região peribrônquica. Resultados: Embora não tenha havido diferenças entre os quatro grupos quanto aos parâmetros de mecânica respiratória avaliados, houve aumento da Lm no grupo FC + EPP. O número de células positivas para MAC-2 na região peribrônquica e no parênquima pulmonar distal foi maior no grupo FC + EPP do que nos outros grupos, assim como o foi o número de células positivas para MMP-12 e gp91phox, porém somente no parênquima pulmonar distal. Conclusões: Nosso modelo de enfisema induzido por instilação de EPP e exposição a FC resulta em um grau significativo de destruição parenquimatosa em um período de tempo menor que o empregado em outros modelos de enfisema induzido por FC, o que reforça a importância do desequilíbrio entre proteases e antiproteases e entre oxidantes e antioxidantes na patogênese do enfisema.

ABSTRACT Objective: To describe a murine model of emphysema induced by a combination of exposure to cigarette smoke (CS) and instillation of porcine pancreatic elastase (PPE). Methods: A total of 38 C57BL/6 mice were randomly divided into four groups: control (one intranasal instillation of 0.9% saline solution); PPE (two intranasal instillations of PPE); CS (CS exposure for 60 days); and CS + PPE (two intranasal instillations of PPE + CS exposure for 60 days). At the end of the experimental protocol, all animals were anesthetized and tracheostomized for calculation of respiratory mechanics parameters. Subsequently, all animals were euthanized and their lungs were removed for measurement of the mean linear intercept (Lm) and determination of the numbers of cells that were immunoreactive to macrophage (MAC)-2 antigen, matrix metalloproteinase (MMP)-12, and glycosylated 91-kDa glycoprotein (gp91phox) in the distal lung parenchyma and peribronchial region. Results: Although there were no differences among the four groups regarding the respiratory mechanics parameters assessed, there was an increase in the Lm in the CS + PPE group. The numbers of MAC-2-positive cells in the peribronchial region and distal lung parenchyma were higher in the CS + PPE group than in the other groups, as were the numbers of cells that were positive for MMP-12 and gp91phox, although only in the distal lung parenchyma. Conclusions: Our model of emphysema induced by a combination of PPE instillation and CS exposure results in a significant degree of parenchymal destruction in a shorter time frame than that employed in other models of CS-induced emphysema, reinforcing the importance of protease-antiprotease imbalance and oxidant-antioxidant imbalance in the pathogenesis of emphysema.

OBJETIVO: Descrever um novo modelo murino de enfisema induzido pela fumaça de cigarro. MÉTODOS: Vinte e quatro ratos Wistar foram divididos em dois grupos: o grupo fumaça de cigarro, com 12 ratos expostos à fumaça de 12 cigarros comerciais com filtro três vezes ao dia (um total de 36 cigarros por dia), sete dias por semana, durante 30 semanas e o grupo controle, com 12 animais expostos ao ar ambiente três vezes ao dia, sete dias por semana, durante 30 semanas. A função pulmonar foi avaliada por meio de ventilação mecânica, e o enfisema foi morfometricamente avaliado por meio do diâmetro alveolar médio (Lm). RESULTADOS: A média de ganho de peso foi significativamente menor (aproximadamente dez vezes menor) no grupo fumaça de cigarro do que no grupo controle. O Lm foi 25.0% maior no grupo fumaça de cigarro. Os parâmetros de função pulmonar tenderam a ser piores no grupo fumaça de cigarro. CONCLUSÕES: O novo modelo murino de enfisema induzido pela fumaça de cigarro e a metodologia empregada neste estudo são eficazes e reproduzíveis; são, portanto, uma opção promissora e economicamente viável para estudos sobre a fisiopatologia e o tratamento da DPOC.

OBJECTIVE: To describe a new murine model of cigarette smoke-induced emphysema. METHODS: Twenty-four male Wistar rats were divided into two groups: the cigarette smoke group, comprising 12 rats exposed to smoke from 12 commercial filter cigarettes three times a day (a total of 36 cigarettes per day) every day for 30 weeks; and the control group, comprising 12 rats exposed to room air three times a day every day for 30 weeks. Lung function was assessed by mechanical ventilation, and emphysema was morphometrically assessed by measurement of the mean linear intercept (Lm). RESULTS: The mean weight gain was significantly (approximately ten times) lower in the cigarette smoke group than in the control group. The Lm was 25.0% higher in the cigarette smoke group. There was a trend toward worsening of lung function parameters in the cigarette smoke group. CONCLUSIONS: The new murine model of cigarette smoke-induced emphysema and the methodology employed in the present study are effective and reproducible, representing a promising and economically viable option for use in studies investigating the pathophysiology of and therapeutic approaches to COPD.

OBJECTIVE: To verify the accordance of functional and morphometric parameters during the development of emphysema. METHODS: BALB/c mice received a nasal drop of either papain or saline solution and were studied after 1, 3, 15, 28, and 40 days. Functional parameters, such as airway resistance, tissue damping, and tissue elastance, were analyzed. To evaluate the structural changes and possible mechanisms involved in this disease, we measured the mean linear intercept, the volume proportions of elastic and collagen fibers, the number of macrophages, the numbers of cells expressing metalloprotease 12 and 8-isoprostane in lung parenchyma. RESULTS: We only observed decreases in tissue elastance and tissue damping on the 28th day, with a concomitant increase in the mean linear intercept, indicating the presence of emphysema. However, only the mean linear intercept values remained increased until the 40th day. The volume proportion of collagen fibers was increased from the 15th day to the 40th day, whereas the volume proportion of elastic fibers was only increased on the 40th day. The number of macrophages increased beginning on the 1st day. The expression of metalloproteinase 12 was increased from the 3rd day until the 40th day. However, 8-isoprostane expression was only increased on the 1st and 3rd days. CONCLUSIONS: In this study, morphometric parameters were found to be more reliable for detecting the presence of emphysema than the functional parameters measured by respiratory mechanics. Further investigations are necessary to understand how the extracellular matrix remodeling observed in the lung parenchyma could be involved in this process.