Sepsis and mechanical ventilation alter the tight junction proteins in rat lungs in vivo

Abstract

Introduction: The tight junction (TJ) complexes of the alveolar epithelium regulate lung permeability. Objectives: To determine whether sepsis and mechanical ventilation alter the TJ complexes in the alveolar walls of rat lungs in vivo. Methods: We performed an abdominal sepsis model induced by cecal ligation and puncture (CLP) followed 24 h later by mechanical ventilation (MV) with a protective strategy (Vt= 9 ml/kg+PEEP 5 cmH2O for 4 h) in adult rats (Sprague-Dawley). The groups were (n= 10/group): Sham-without MV (laparotomy only, control group), CLP-without MV, Sham+MV and CLP+MV. We collected lung tissue, bronchoalveolar lavage fluid (BALF) and plasma and we measured the levels of Occludin and ZO1 (ELISA, inmunofluorescence), cytokines (ELISA) and apoptosis (caspase 3 and TUNEL). Results: 1) The levels of cytokines were similar in all groups, except for a decrease of IL1b in the BALF of the CLP+MV group. 2) Compared with the control group, the activity of caspase 3 and apoptosis in rat lungs was increased in the CLP, MV and CLP+MV groups. 3) Compared with the control group, the levels of occludin were increased in the lungs of rats with CLP (with or without MV). Only the combination of CLP and MV increased the levels of occludin in BALF and plasma. In contrast, ZO1 levels decreased in rat lungs after CLP, MV or CLP+MV. In CLP-without MV rats, ZO1 levels increased in the BALF and decreased in plasma. Conclusions: Abdominal sepsis and MV with a protective strategy cause apoptosis and alter the expression of TJ proteins in the lung without modifying the expression of cytokines. Changes in the levels of the TJ proteins in BALF and plasma could be used as diagnostic biomarkers in acute lung injury.