Desenvolvimento de lesão pulmonar aguda induzida por instilação intratraqueal de lipopolissacáride em um modelo animal de enfisema pulmonar por administração de elastase

Abstract

Introduction: The response of lungs with emphysema to an acute lung injury (ALI) remains unclear. The aim of this study was to compare the severity of ALI in response to intratracheal instillation of lipopolysaccharide (LPS) in rats with and without emphysema. Methods: Twenty four adult male Wistar rats were randomized to four groups: control group (C-G), ALI group (ALI-G), emphysema group (E-G), emphysema and ALI group (E-ALI-G). The emphysema was induced by intratracheal instillation of elastase (12 UI). After three weeks, the animals of ALI groups received LPS intratracheally(2 mg/Kg). Euthanasia and the following analysis were performed 24 hours after ALI induction: blood gas measures, bronchoalveolar lavage (BAL), mRNA expression of inflammatory mediators and lung histology. Results: The animals of ALI-G (0.55 ± 0.15) and E-ALI-G (0.69 ± 0.08) showed a higher ALI score compared to C-G (0.12 ± 0.04) and E-G (0.16 ± 0.04) (p <0.05). Total cell count (E-G = 3.09 ± 0.83; ALI-G = 4.45 ± 1.90; E-ALI-G = 5.90 ± 2.10; C-G = 0.73 ± 0.37 x 105) and neutrophil count (E-G = 0.69 ± 0.35; ALI-G = 2.53 ± 1.09; E-ALI-G = 3.86 ± 1.40; C-G = 0.09 ± 0.07 x 105) in the BAL were higher in the groups E-G, ALI-G and E-ALI-G when compared to C-G (p <0.05). The IL-6, TNF-α, and CXCL2 mRNA expressions were higher in the animals that received LPS (ALI-G and E-ALI-G) compared to the C-G and E-G (p <0.05). Although there were no statistical differences between the animals with and without emphysema in response to LPS instillation, we observed a trend of higher ALI score and BAL cellularity in the E-ALI-G. The E-ALI-G also showed an increased BAL/serum albumin ratio. Conclusion: The presence of emphysema was associated with a trend of increase in the inflammatory pulmonary response to intratracheal LPS instillation.