Protective Effect Of PPAR γ Pathway On Electro - Acupuncture Preconditioning In Acute Lung Injury And Its Related Mechanism

BackgroundALI (acute lung injury, ALI) is characterized by acute progressive hypoxic respiratory insufficiency caused by direct or indirect non-cardiac factors including severe infection, shock, trauma, inhalation of harmful gas, poisoning and so on. The serious expression of ALI is ARDS (acute respiratory distress syndrome, ARDS). It is due to serious imbalance of inflammatory response in local (lung) or other visceral organs (system), which leads to the barrier damage of alveolar epithelia and vascular endothelia, thereby causing acute inflammation in the lung and pulmonary edema rich in proteins. A lot of studies suggest that the imbalance of inflammatory reaction is one of the main mechanisms for acute lung injury. For the present, except for that the effect on the treatment of ALI by mechanical ventilation is definite; there are no other effective treatments in clinical practice, especially medications. Therefore, the mortality has been high, and the prevention and treatment of acute lung injury are an important research issues on perioperative organic protection. In recent years, some studies have found that peroxisome proliferator-activated receptor (PPARγ) exhibits comprehensive anti-inflammatory and organ protective effect. It is an important anti-inflammatory system and closely related to NF-κB proinflammatory system. The combinations of two systems constitute the inflammatory signaling pathways and maintain the balance of inflammatory response. Our former study found that pretreatment by acupoint electroacupuncture could significantly alleviate acute lung injury, but the exact mechanism was unclear. Possibly it was associated with the inflammatory signal regulating pathway of PPARγ-NF κB.Purpose1. We performed studies to explore the interventional effect of electroacupuncture pretreatment against ALI and confirm the protective role of PPARγ regulatory pathway on ALI through measuring PPARy and its downstream NF-κB and relevant Pro-inflammatory cytokines such as TNF-α、IL-1β and IL-6.2. To further elucidate out of control inflammation mechanisms of ALI and clarify the protective effect and possible mechanisms on electroacupuncture pretreatment against acute lung injury. Maybe a new thread on ALI treatment will be provided.Methods1. Establishing rat models of acute lung injury caused by lipopolysaccharide. Comparing the effects of LPS stimulation on rats at different time.2. Inducing acute lung injury model in rat by lipopolysaccharide (LPS). Comparing the differences among control group, ALI group, EA pretreatment group rosiglitazone group and GW9662 pretreatment group. Observing the protective effect of electrical stimulation at hegu acupoint on acute lung injury:Lung histopathological score, lung wet to dry weight ratio (W/D), arterial blood gas analysis.3. Comparing the differences among control group, ALI group, EA pretreatment group, rosiglitazone group and GW9662 pretreatment blocker group. Evaluating the inhibitory effect of electrical acupuncture at Hegu acupoint on inflammatory cytokines by ELISA:TNF-α, IL-6 and IL-1β in bronchoalveolar lavage.4. Collecting rat lung tissue samples and exploring the mechanism of PPARy-NF κB pathway against acute lung injury by detecting PPARy and NF-κB expression level by westernblot.Results1. PaO2 decreased gradually after LPS stimulation and dropped to the lowest at 4h. Meanwhile, the lung tissue pathological score and W/D ratio increased with time with the peak at 4h after LPS treatment.2. Pathological section suggested the ALI degree in EA pretreatment group was lighter compared to that in ALI group and pathological scores also confirmed this. ALI degree in Rosiglitazone group had a strong resemblance of that in EA group and was lighter than that in ALI group as well. Additionally, EA as well as Rosiglitazone pretreatment alleviated pulmonary edema compared to solely LPS treatment based on the statistical analysis of W/D.3. Cytokine TNF-α, IL-6 and IL-1β were inhibited in EA pretreatment group and Rosiglitazone group(P<0.05) compared to LPS group.4. Hegu electroacupuncture pretreatment upregulated PPARy expression and inhibited NF-κB expression.Conclusions1. Electroacupuncture pretreatment at Hegu acupoint have protective effect on acute lung injury in rats.2. EA treatment acts through promoting PPARy expression, inhibiting NF-κB expression and then NF-κB signaling pathway downregulates related inflammatory cytokines to play a protective role against ALI.