Mesenteric Lymph Duct Drainage Attenuates Acute Lung Injury in Rats with Severe Intraperitoneal Infection

The purpose of this study is to investigate the hypothesis that the mesenteric lymphatic system plays an important role in acute lung injury in a rat model induced by severe intraperitoneal infection. Male Wistar rats weighing 250 ∼ 300 g were randomly divided into 3 groups and subjected to sham operation, intraperitoneal infection, or mesenteric lymphatic drainage. The activity of diamine oxidase (DAO) and myeloperoxidase (MPO) were measured by enzymatic assay. The endotoxin levels in plasma, lymph, and bronchoalveolar lavage fluid (BALF) were evaluated using the limulus amoebocyte lysate reagent. The cytokines, adhesion factors, chemokines, and inflammatory factors were detected by ELISA. TLR-4, NF-kB, and IRAK-4 were analyzed by Western blotting. Compared with sham-operated rats, rats with intraperitoneal infection had increased MPO and decreased DAO activity in intestinal tissues. Mesenteric lymph drainage reduced the alterations in MPO and DAO activity induced by intraperitoneal infection. The MPO activity in pulmonary tissue and the permeability of pulmonary blood vessels were also increased, which were partially reversed by mesenteric lymph drainage. The endotoxin levels in lymphatic fluid and alveolar perfusion fluid were elevated after intraperitoneal infection but decreased to control levels after lymph drainage. No alterations in the levels of plasma endotoxin were observed. The number of neutrophils was increased in BALF and lymph in the infected rats, and was also reduced after drainage. Lymph drainage also decreased the levels of inflammatory cytokines, chemokines, and adhesion factors in the plasma, lymph, and BALF, as well as the levels of TLR-4, NF-kB, and IRAK-4 in pulmonary and intestinal tissues. The mesenteric lymphatic system is the main pathway involved in early lung injury caused by severe intraperitoneal infection, in which activation of the TLR-4 signal pathway may play a role.