Investigation Of The Relationship Between HSP70 And TLR4-NF-κB Pathway During The Pathogenesis Of Acute Lung Injury

Objective: To investigate the possible relationship between HSP70 and TLR4-NF-κB during the pathogenesis of acute lung injury(ALI), Wistar rat model was built by tail vein injection of lipopolysaccharide(LPS). The heat shock protein 70(HSP70), Toll like receptor 4(Toll-like receptor 4, TLR4) TLR4, nuclear transcription factor kappa B(NF-κB) and the expression of inflammatory cytokines were detected to explore the mutual regulation between HSP70 and TLR4/NF-κB signaling pathway in the pathogenesis of ALI.Methods: Wistar rats were selected as experimental animal, 48 rats were randomly divided into two groups: normal saline control group(group NS, 24 rats), acute lung injury model group(group LPS, 24), LPS group was subdivided into three subgroup by different timelength(2h/6h/24h), each group has 8 rats. By tail vein injection of LPS(6mg/kg.body weight) preparation of acute lung injury model, rats were measured in arterial blood gas analysis at different time points. Part of lung tissue was fixed to observate the microstructure changes of lung tissue by HE staining. Part of lung tissue was used to test the lung tissue wet/dry weight ratio. Serum were collected to detect the released level of TNF-α、IL-6、IL-10 by enzyme-linked immunosorbent assay(ELISA). Realtime-PCR was used to analyse the expression of HSP70、TLR4 and NF-κB m RNA in lung tissue.Results: Compared with the NS group, LPS group showed persistent hypoxemia, Pa O2 decreased with the extension of the time, and the ratio of W/D in the lung tissue increased with the extension of the time. There were significant differences(P<0.05) between the NS and LPS groupcontrol group at each time point. The results of HE staining under light microscope observation showed the pulmonary septal thickening, interstitial edema, inflammatory cell infiltration and extravasation of red blood cells, alveolar lumen narrowed, visible inflammatory lung injury. Analysis of lung tissue pathology score using semi quantitative indicated that the pathological damage score increased with the time prolonged. The expression of TNF-α, IL-6, IL-10 in serum of LPS goup was significantly increased compared with the NS group. At the same time, the expression level of HSP70 in the lung tissue gradually increased, up to a peak at 24 h. Along with the time of the LPS treatment, the m RNA expression of HSP70 in lung tissues, TLR4 and NF-κB were gradually increased in LPS group, the expression of HSP70、TLR4 and NF-κB has a positive correlation with the time point forward(P<0.05).Conclusion: A rat model of acute lung injury can be successfully established by tail vein injection of LPS(6mg/kg). There is positive correlation between HSP70 and TLR4-NF-κB pathway and during the pathogenesis of ALI and HSP70 has certain protective effect on the lung tissue.