Characteristics of Neutrophils Infiltration in Ventilation-induced Lung Injury

Neutrophils play a critical role in ventilation-induced lung injury. This study was aimed to investigate the characteristics of neutrophils influx in lungs induced by high tidal volume ventilation. Anaesthetized rats were randomly divided into low tidal volume ventilation group (Vt: 7 mL/kg, LV group) or high tidal volume ventilation group (Vt:42mL/kg, HV group ) (n=40 in each). Rats in each group were ventilated for 0, 60, 90, 120 and 240 min. The wet/dry lung weight ratio (W/D) was measured. The levels of macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-α (TNF-α), and the activity of myeloperoxidase (MPO) were detected by enzyme-linked immunosorbent assay (ELISA). The number of neutrophils in bronchoalveolar lavage fluid (BALF) was counted after Wright’s staining, and the percentage of netrophils in lung tissues calculated. Histopatholgical examination was used to observe the changes of lung tissues after different ventilations. The results showed that the W/D weight ratio was increased, and the levels of MIP-2 and TNF-α significantly enhanced in HV group at 90, 120 and 240 min. Neutrophils in BALF and the neutrophil percentage in lung tissues were also elevated at 120 and 240 min, which coincided with the enhanced activity of MPO in HV group. The lung injury was significantly related with the ventilation time and the infiltration of neutrophils in lungs in HV group. In conclusion, in ventilation-induced lung injury, neutrophil infiltration is present in a time-dependent manner and associated with the aggravated lung injury. Pulmonary structural damage may be the main reason for ventilation-induced lung injury.

Role of Glutamine in the Mediation of E-cadherin, p120-catenin and Inflammation in Ventilator-induced Lung Injury

Background： Ventilator-induced lung injury （VILI） is commonly associated with barrier dysfunction and inflammation reaction. Glutamine could ameliorate VILI, but its role has not been fully elucidated, This study examined the relationship between inflammatory cytokines （interleukin JILl-6, tumor necrosis factor [TNF]-α, and IL-10） and adherens junctions （E-cadherin, p 120-catenin）, which were ameliorated by glutamine in VILI, both in vitro and in vivo. Methods： For the in vivo study, 30 healthy C57BL/6 mice weighing 25-30 g were randomly divided into five groups with random number table （n = 6 in each group）： control （Group C）; low tidal volume （Group L）; low tidal volume ＋ glutamine （Group L ＋ G）; high tidal volume （Group H）; and high tidal volume ＋ glutamine （Group H ＋ G）. Mice in all groups, except Group C, underwent mechanical ventilation for 4 h. For the in vitro study, mouse lung epithelial 12 （MLE- 12） cells pretreated with glutamine underwent cyclic stretching at 20% for 4 h. Cell lysate and lung tissue were obtained to detect the junction proteins, inflammatory cytokines, and lung pathological changes by the Western blotting, cytokine assay, hematoxylin and eosin staining, and immunofluorescence. Results： In vivo, compared with Group C, total cell counts （t= -28.182, P 〈 0.01）, the percentage of neutrophils （t = -28.095, P 〈 0.01）, IL-6 （t = -28.296, P 〈 0.01 ）, and TNF-α（t = - 19.812, P 〈 0.01 ） in bronchoalveolar lavage （BAL） fluid, lung injury scores （t = -6.708, P 〈 0.01）, and the wet-to-dry ratio （t = - 15.595, P 〈 0.01 ） were increased in Group H; IL- 10 in BAL fluid （t = 9.093, P 〈 0.01 ） and the expression of E-cadherin （t= 10.044, P 〈 0.01） and p120-catenin （t = 13.218, P 〈 0.01） were decreased in Group H. Compared with Group H, total cell counts （t - 14.844, P 〈 0.01 ）, the percentage of neutrophils （t = 18.077, P 〈 0.0 l ）, IL-6 （t - 18.007, P 〈 0.01 ）, and TNF-α （t =1 0.171, P 〈 0.01 ） in BAL fluid were decreased in Group H ＋ G; IL-10 in BAL fluid （t - -7.531, P 〈 0.01 ） and the expression of E-cadherin （t = - 14.814, P 〈 0.01 ） and p 120-catenin （t = -9.114, P 〈 0.01 ） were increased in Group H ＋ G. In vitro, compared with the nonstretching group, the levels of IL-6 （t = 21.111, P 〈 0.01 ） and TNF-α （t - 15.270, P 〈 0.01 ） were increased in the 20% cyclic stretching group; the levels of IL- 10 （t = 5.450, P 〈 0.01 ） and the expression of E-cadherin （t = 17.736, P 〈 0.01 ） and p 120-catenin （t = 16.136, P 〈 0.01 ） were decreased in the 20% cyclic stretching group. Compared with the stretching group, the levels of IL-6 （t = 11.818, P 〈 0.01） and TNF-α （t = 8.631, P 〈 0.01 ） decreased in the glutamine group; the levels of IL- 10 （t = 3.203, P 〈 0.05） and the expression of E-cadherin （t= 13.567, P 〈 0.01） and p 120-catenin （t = -10.013, P 〈 0.01） were increased in the glutamine group. Conclusions： High tidal volume mechanical ventilation and 20% cyclic stretching could cause VIM. Glutamine regulates VIM by improving cytokines and increasing the adherens junctions, protein E-cadherin and p 120-catenin, to enhance the epithelial barrier function.