The Effect And Mechanisms Of Tight Junction Protein Occludin In Ventilation Induced Lung Injury

Objective Ventilation-induced lung injury is characterized by increased alveolar-capillary permeability which can induce theinfluxion of protein-riched edema fluid and inflammatory cells into lung alveoli. The root cause was the integrity of the alveolar membrane was damaged and permeability was changed. Occludin, as a tight junction protein, plays an important role in maintaining the integrity of lung epithelial barrier. The tight junction proteinsmainly insist of ZO-1,2,3, tight junction protein (Claudin) and atresia protein (Occludin). Studies have shown that stimulation of the inflammation, calcium, hydrogen peroxide, etc., can active the intracellular protein kinases such as PKC, Src and protein phosphatases of PP2A,PPl,the effect on Occludin to make it phosphorylation or dephosphorylation, which regulate cell TJ degradation or formation. This study established a mechanical ventilation induced lung injury model with different tidal volume to explore the effects and mechanisms of Occludin in ventilation induced lung injury.Methods Thirty specific-pathogen free (SPF) Wistar rats,15females and15males, weighing250-300g, were randomly divided into5groups(n=6):the control group(group C), the low tidal volume group(group L), the low tidal volume and PKC inhibitors(group L+P), the high tidal volume(group H), the high tidal volume and PKC inhibitor(group H+P). All rats were fasted for12hours before the experiment, and free access to water. Rats were anesthetized by intraperitoneal injection of10%chloral hydrate (3.5ml/kg).The rats in group C were only tracheotomy surgery without mechanical ventilation, the other four groups were mechanically ventilated for4hours. The rats in groups L+P and H+P were injectedwith PKC inhibitor (Bisindolylmaleimide I,0.12mg/kg) through muscle one hour before anesthesia.Rats were sacrificed after mechanical ventilation. Specimens of lung tissues were harvested. Lung pathological changes were observed with optical microscope, and lung wet/dry weight ratio was measured. The Occludin protein level was assayed with Immunohistochemistry staining and Western blot.Results HE staining and Immunohistochemistry results showed that Occludin mainly located in the alveolar endothelial cells and some alveolar epithelial cells in the control group. Observed the lung pathophysiological changes under optical microscope found the lung tissue pathology injury was much seriously in group L and H. Compared with group C, lung wet/dry weight ratio of the other four groups was increased while the expression of Occludin protein was reduced (P<0.05). Compared with group S, the lung W/D ratio was increased but the expression of Occludin protein reduced in group L, while the lung W/D ratio was reduced but the expression of Occludin protein increased in group S+P (P<0.01). Compared with group H, the lung W/D ratio was reduced and the expression of Occludin protein increased in group L+P (P<0.01), the results have the statistical meaning.Conclusion Large volume mechanical ventilation results in severe lung injury. Mechanical ventilation activated the PKC signaling pathway, up-regulation the Occludin expression can reduce the ventilation induced lung injury.Therefore it considers that the expression of Occludin related to ventilation induced lung injury.