| ObjectiveTo observe the effects of dexmedetomidine on the pathological change, the content of TNF-α and IL-6,the expression of TLR-4、p-AKT and collagen synthesis in the lung tissue in rats with acute respiratory distress syndrome(ARDS) induced by lipopolysaccharide(LPS), and moreover, explore the effect of dexemetomidine on early stage anti-fibrosis and the potential mechanism in rats with LPS-induced ARDS. MethodsFifty-four male rats were randomly divides into 3 groups(n=18 each): control group(Ct group)、LPS group and LPS+DEX group(DEX group). Each group was further divides into 1d、3d and 7d group(n=6 each). Intra-tracheal inhalation of LPS(5 mg/kg) of LPS group and DEX group, Ct group intra-tracheal inhalation of equivalent saline. DEX group intra-peritoneal injection of dexemetomidine(25 μg/kg) twice a day after intra-tracheal inhalation, and at the same time points, Ct group and LPS group intra-peritoneal administration with equivalent saline. Arterial blood samples were taken after intra-peritoneal administration with 10% chloral hydrate, lung tissues were to be seized after the animals were sacrificed.The pathological changes of the lung tissues were obtained by HE and MASSON staining. The level of α-SMA expression was analyzed by immunohistochemistry. The levels of TNF-α、IL-6、HYP and Co1 I in lung tissues were detected with ELISA.TLR4、integrin-β1 and p-AKT expression in lung tissues were assayed with western blotting. Results1. Lung tissue pathology results: Ct group showed no abnormal lung tissue pathology. Compared with the same time points of Ct group, LPS-1d group showed alveolar septal widening, capillary and interstitial edema, some alveolar collapse and rupture. LPS-3d group showed alveolar septal getting wider, a lot of inflammatory cells infiltration and erythrocytes leakage, fibroblast proliferation can been seen in rats lung tissues. The results showed the alveolar structure disturbance, alveolar septal rupture, a large number of cells infiltration and formation of fiberboard in LPS-7d group. Compared with the dame time point in LPS-7d group, DEX group rat lung tissue showed inflammatory cell infiltration was lighter, widened alveolar septal and interstitial edema were significantly reduced, only a little fibroblast proliferation and less damage of normal alveolar structure can been seen. The results showed the alveolar structure been green stained slightly by Masson staining in Ct group. Compared with the same time points of Ct group, the alveolar structure of LPS-1d group was green stained heavily, positive staining was further increased to sheet morphology in LPS-3d group, flake and block shape were seen in LPs-7d group. Compared with LPS-7d group, the DEX-7d group green staining of alveolar septal was decreased. Lung collagen volume fraction indicated collagen synthesis was stimulated by LPS in a time-dependent manner. Compared with the same time points of Ct group, the lung collagen volume fraction was significantly higher in LPS-1d group(p < 0.05) and in LPS-3d、7d group(p < 0.01). Dexmedetomidine can significantly inhibit lung tissue fibrosis in rats with ARDS, so the lung collagen volume fraction was significantly lower in DEX-7d group, as compared with LPS-7 group( p< 0.05).2. ELISA results: Compared with Ct group, after receiving LPS intra-tracheal inhalation, the TNF-α and IL-6 levels in rat lung tissue of LPS-1d group and DEX-1d group were significantly increased(p < 0.05), and got the peak value, then gradually decreased. But the TNF-α and IL-6 levels still higher than those at the same time points of Ct group(p < 0.01). The TNF-α and IL-6 levels in rat lung tissue of DEX group were significantly less than that of LPS group at the same time points(p < 0.05).3.Western blotting results: Compared with Ct group, the TLR4、integrin-β1 and p-Akt levels in rat lung tissue of LPS-1d group and DEX-1d group were significantly increased(p < 0.05). In the LPS-3d、7d group and DEX-3d、7d group the results showed : the p-Akt levels were at the peak point, and the TLR4 and integrin-β1 expression were increasing. There was no significantly difference in the AKT level of all groups(p < 0.05). Compared with LPS-7d group, the 7d HYP and Col I levels of DEX-7d group were significantly decreased(p < 0.05).4. ELISA results: Compared with the same time points of Ct group, the HYP and Co1 I levels in rats lung tissues of LPS group and DEX group were significantly increased(p < 0.05). Compared with LPS-7d group, the 7d HYP and Col I levels of DEX-7d group were significantly decreased(p < 0.05).5. Immunohistochemistry results: Compared with Ct-7d group, the α-SMA levels in rat lung tissue of LPS-7d group and DEX-7d group were significantly increased(p < 0.01). Compared with LPS-7d group, the α-SMA level of DEX-7d group was significantly decreased(p < 0.01). Conclusions1.Inflammation response and early stage fibrosis can been seen in the lung tissues of rats with LPS-induced ARDS. The pathophysiology was consistent with ARDS. The results verified the successful establishment of animal models.2.In this study, the results showed that dexmedetomidine can inhibit inflammation response and early stage pulmonary fibrosis in rats with LPS-induced ARDS. It can concluded that the mechanism of anti-fibrosis may be related to inhibiting the inflammation response and oxidative stress, promoting alveolar epithelial repair. Furthermore, it is related to inhibiting the LR4 and PI3k-AKT signaling pathways, down-regulating the integrinβ1 level and decreasing the activation of lung fibroblast cell and collagen secretion. |
