Role of beta-dsfensin-3 in lung tissue in a rat model of ventilator-associated pneumonia

Abstract

Objective To investigate the role of beta-defensin-3 (BD-3) in lung tissue in a rat model of ventilator-associated pneumonia. Methods Twenty pathogen-free male SD rats weighing 240-290 g were randomly divided into 2 groups (n=10 each): non-ventilator-associated pneumonia group (group N) and wentilator-associated pneumonia group (group V). The animals were anesthetized with intraperitoneal (IP) 20% urethane 1.3 g/kg. Oral tracheal intubation was performed under direct vision. In group N the animals kept spontaneous breathing. MRSA suspension (1010 cfu/ml) 0.2 ml was introduced into bronchus immediately after tracheal intubation. The animals were then extubated. In group V the animals were mechanically ventilated (VT 6 ml/kg, RR 88 bpm, PEEP 5 cm H2O, FiO2 21%) for 4 h. MRSA suspension (1010 cfu/ml) 0.2 ml was introduced into bronchus at the end of 4 h mechanical ventilation. The animals were killed at 48 h after inoculation in both groups. The lungs were removed for microscopic examination of pathologic changes which were scored. Wet lung weight/body weight ratio (WW/BW) was measured. Lung bacterial counts and spleen eulture were performed. The expression of BD-3 in lung tissue was detected by immuno-histochemical staining. Results WW/BW, lung pathology scores, lung bacterial counts and the incidence of bacteremia were significantly higher in group V than in group N, while BD-3 expression in lung tissue was significantly lower in group V than in group N. Conclusion The pathogenesis of ventilator-associated pneumonia is related to the down-regulation of BD-3 expression in rat lung tissue. Key words: Respiration, artificial; Pneumonia, baeterial; beta-Defensins